+ maps2-export-page-index-in-kpagemap.patch added to -mm tree

+ maps2-export-page-index-in-kpagemap.patch added to -mm tree

[akpm]

The patch titled
     maps2: export page index in kpagemap
has been added to the -mm tree.  Its filename is
     maps2-export-page-index-in-kpagemap.patch

*** Remember to use Documentation/SubmitChecklist when testing your code ***

See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this

------------------------------------------------------
Subject: maps2: export page index in kpagemap
From: Fengguang Wu <wfg@mail.ustc.edu.cn>

To analyze/optimize the memory footprint, the number one question people
may ask about pagemap/kpagemap could be:

	Which part of the files are being actively mapped?

In the (rare) case of nonlinear mapping, that question could only be
answered by explicitly exporting the page index in kpagemap.  Simply
judging by the PFNs from pagemap could be wrong!

Cc: Matt Mackall <mpm@selenic.com>
Cc: John Berthels <jjberthels@gmail.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/proc/proc_misc.c |   15 +++++++++------
 1 files changed, 9 insertions(+), 6 deletions(-)

diff -puN fs/proc/proc_misc.c~maps2-export-page-index-in-kpagemap fs/proc/proc_misc.c
--- a/fs/proc/proc_misc.c~maps2-export-page-index-in-kpagemap
+++ a/fs/proc/proc_misc.c
@@ -672,8 +672,8 @@ static const struct file_operations proc
 #endif
 
 #ifdef CONFIG_PROC_PAGE_MONITOR
-#define KPMSIZE (sizeof(unsigned long) * 2)
-#define KPMMASK (KPMSIZE - 1)
+#define KPMITEMS 3
+#define KPMSIZE (sizeof(unsigned long) * KPMITEMS)
 /* /proc/kpagemap - an array exposing page flags and counts
  *
  * Each entry is a pair of unsigned longs representing the
@@ -699,7 +699,7 @@ static ssize_t kpagemap_read(struct file
 
 	pfn = src / KPMSIZE - 1;
 	count = min_t(unsigned long, count, ((max_pfn + 1) * KPMSIZE) - src);
-	if (src & KPMMASK || count & KPMMASK)
+	if (src % KPMITEMS || count % KPMITEMS)
 		return -EIO;
 
 	page = (unsigned long *)__get_free_page(GFP_USER);
@@ -713,25 +713,28 @@ static ssize_t kpagemap_read(struct file
 		if (pfn == -1) {
 			page[0] = 0;
 			page[1] = 0;
+			page[2] = 0;
 			((char *)page)[0] = (ntohl(1) != 1);
 			((char *)page)[1] = PAGE_SHIFT;
 			((char *)page)[2] = sizeof(unsigned long);
 			((char *)page)[3] = KPMSIZE;
-			i = 2;
+			i = KPMITEMS;
 			pfn++;
 		}
 
-		for (; i < 2 * chunk / KPMSIZE; i += 2, pfn++) {
+		for (; i < KPMITEMS * chunk / KPMSIZE; i += KPMITEMS, pfn++) {
 			ppage = pfn_to_page(pfn);
 			if (!ppage) {
 				page[i] = 0;
 				page[i + 1] = 0;
+				page[i + 2] = 0;
 			} else {
 				page[i] = ppage->flags;
 				page[i + 1] = atomic_read(&ppage->_count);
+				page[i + 2] = page_index(ppage);
 			}
 		}
-		chunk = (i / 2) * KPMSIZE;
+		chunk = (i / KPMITEMS) * KPMSIZE;
 
 		if (copy_to_user(buf, page, chunk)) {
 			ret = -EFAULT;
_

Patches currently in -mm which might be from wfg@mail.ustc.edu.cn are

readahead-compacting-file_ra_state.patch
readahead-mmap-read-around-simplification.patch
readahead-combine-file_ra_stateprev_index-prev_offset-into-prev_pos.patch
readahead-combine-file_ra_stateprev_index-prev_offset-into-prev_pos-fix.patch
readahead-combine-file_ra_stateprev_index-prev_offset-into-prev_pos-fix-2.patch
radixtree-introduce-radix_tree_next_hole.patch
readahead-basic-support-of-interleaved-reads.patch
readahead-remove-the-local-copy-of-ra-in-do_generic_mapping_read.patch
readahead-remove-several-readahead-macros.patch
readahead-remove-the-limit-max_sectors_kb-imposed-on-max_readahead_kb.patch
filemap-trivial-code-cleanups.patch
filemap-convert-some-unsigned-long-to-pgoff_t.patch
make-swappiness-safer-to-use.patch
maps2-export-page-index-in-kpagemap.patch
maps-pssproportional-set-size-accounting-in-smaps.patch
convert-ill-defined-log2-to-ilog2.patch
seqfile-merge-duplite-code-to-seq_open_private.patch
avoid-negative-and-full-width-shifts-in-radix-treec.patch

Re: + maps2-export-page-index-in-kpagemap.patch added to -mm tree

[Dave Hansen]

On Mon, 2007-09-24 at 13:44 -0700, akpm@linux-foundation.org wrote:
> 
> 
> To analyze/optimize the memory footprint, the number one question
> people
> may ask about pagemap/kpagemap could be:
> 
>         Which part of the files are being actively mapped?
> 
> In the (rare) case of nonlinear mapping, that question could only be
> answered by explicitly exporting the page index in kpagemap.  Simply
> judging by the PFNs from pagemap could be wrong! 

I'll look over this in some more detail, but I have the feeling KPMSIZE
reintroduces the overrunning of users' buffers bug.  

-- Dave

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: + maps2-export-page-index-in-kpagemap.patch added to -mm tree

[Dave Hansen]

On Mon, 2007-09-24 at 15:59 -0500, Matt Mackall wrote:
> 
> If we really must do this, it'd be better to have a parallel file with
> the offsets.

Yeah, I'd much rather have a couple of files with really, really simple
and _stable_ formats than one with a more complex and variable one.  

Although you can't answer the "which parts are mapped" question without
the page_index() information, you can answer the "what percentage of
this file is actively mapped" question.

Could someone elaborate a little bit more on exactly why you'd want to
know which parts of the file are mapped? 

-- Dave

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: + maps2-export-page-index-in-kpagemap.patch added to -mm tree

[Matt Mackall]

On Mon, Sep 24, 2007 at 02:23:08PM -0700, Dave Hansen wrote:
> On Mon, 2007-09-24 at 15:59 -0500, Matt Mackall wrote:
> > 
> > If we really must do this, it'd be better to have a parallel file with
> > the offsets.
> 
> Yeah, I'd much rather have a couple of files with really, really simple
> and _stable_ formats than one with a more complex and variable one.  
> 
> Although you can't answer the "which parts are mapped" question without
> the page_index() information, you can answer the "what percentage of
> this file is actively mapped" question.
> 
> Could someone elaborate a little bit more on exactly why you'd want to
> know which parts of the file are mapped? 

Google codesearch finds one actual user of remap_file_pages (and
-lots- of false positives) in an obscure webserver, so I think the
answer somehow involves Oracle.

-- 
Mathematics is the supreme nostalgia of our time.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: + maps2-export-page-index-in-kpagemap.patch added to -mm tree

[Dave Hansen]

On Mon, 2007-09-24 at 16:35 -0500, Matt Mackall wrote:
> On Mon, Sep 24, 2007 at 02:23:08PM -0700, Dave Hansen wrote:
> > Could someone elaborate a little bit more on exactly why you'd want to
> > know which parts of the file are mapped? 
> 
> Google codesearch finds one actual user of remap_file_pages (and
> -lots- of false positives) in an obscure webserver, so I think the
> answer somehow involves Oracle.

If you're asking yourself wtf Oracle is doing, I can see how this is
helpful.  But, since Oracle has to maintain its own internal mappings of
what it remapped, this shouldn't help Oracle itself.

In any case, even if you realize that Oracle is misusing
(under-utilizing?) its remapped areas, what do you do?  You have to go
dig into Oracle to find out what it was doing.  That is precisely what
you would have had to do in the first place without this patch.  I don't
quite get what this buys us. 

-- Dave

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: + maps2-export-page-index-in-kpagemap.patch added to -mm tree

[Matt Mackall]

On Mon, Sep 24, 2007 at 02:50:36PM -0700, Dave Hansen wrote:
> On Mon, 2007-09-24 at 16:35 -0500, Matt Mackall wrote:
> > On Mon, Sep 24, 2007 at 02:23:08PM -0700, Dave Hansen wrote:
> > > Could someone elaborate a little bit more on exactly why you'd want to
> > > know which parts of the file are mapped? 
> > 
> > Google codesearch finds one actual user of remap_file_pages (and
> > -lots- of false positives) in an obscure webserver, so I think the
> > answer somehow involves Oracle.
> 
> If you're asking yourself wtf Oracle is doing, I can see how this is
> helpful.  But, since Oracle has to maintain its own internal mappings of
> what it remapped, this shouldn't help Oracle itself.
> 
> In any case, even if you realize that Oracle is misusing
> (under-utilizing?) its remapped areas, what do you do?  You have to go
> dig into Oracle to find out what it was doing.  That is precisely what
> you would have had to do in the first place without this patch.  I don't
> quite get what this buys us. 

Indeed. In theory, you can do lots of interesting things with
remap_file_pages, but most of them translate into "kludge to get
around limited address space".

I think Fengguang is just thinking forward to the next logical step
here which is "expose what's in the page cache". Which means being
able to go from page back to device:inode:offset or (better, but
trickier) path:offset.

-- 
Mathematics is the supreme nostalgia of our time.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: + maps2-export-page-index-in-kpagemap.patch added to -mm tree

[Fengguang Wu]

On Mon, Sep 24, 2007 at 05:02:02PM -0500, Matt Mackall wrote:
> I think Fengguang is just thinking forward to the next logical step
> here which is "expose what's in the page cache". Which means being

I have been doing it for a long time - that's the filecache patch I
sent you. However it's not quite ready for a public review.

> able to go from page back to device:inode:offset or (better, but
> trickier) path:offset.

It's doing the other way around - a top-down way.

First, you get a table of all cached inodes with the following fields:
  device-number  inode-number  file-path  cached-page-count  status

Then, one can query any file he's interested in, and list all its
cached pages in the following format:
  index  length  page-flags  reference-count
(Sorry, it's the same format I have proposed in the pmaps interface.)

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: + maps2-export-page-index-in-kpagemap.patch added to -mm tree

[Fengguang Wu]

On Mon, Sep 24, 2007 at 05:02:02PM -0500, Matt Mackall wrote:
> I think Fengguang is just thinking forward to the next logical step
> here which is "expose what's in the page cache". Which means being

I have been doing it for a long time - that's the filecache patch I
sent you. However it's not quite ready for a public review.

> able to go from page back to device:inode:offset or (better, but
> trickier) path:offset.

It's doing the other way around - a top-down way.

First, you get a table of all cached inodes with the following fields:
  device-number  inode-number  file-path  cached-page-count  status

Then, one can query any file he's interested in, and list all its
cached pages in the following format:
  index  length  page-flags  reference-count
(Sorry, it's the same format I have proposed in the pmaps interface.)

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: + maps2-export-page-index-in-kpagemap.patch added to -mm tree

[Balbir Singh]

Fengguang Wu wrote:
> On Mon, Sep 24, 2007 at 05:02:02PM -0500, Matt Mackall wrote:
>> I think Fengguang is just thinking forward to the next logical step
>> here which is "expose what's in the page cache". Which means being
> 
> I have been doing it for a long time - that's the filecache patch I
> sent you. However it's not quite ready for a public review.
> 
>> able to go from page back to device:inode:offset or (better, but
>> trickier) path:offset.
> 
> It's doing the other way around - a top-down way.
> 
> First, you get a table of all cached inodes with the following fields:
>   device-number  inode-number  file-path  cached-page-count  status
> 
> Then, one can query any file he's interested in, and list all its
> cached pages in the following format:
>   index  length  page-flags  reference-count

This design sounds good to me, I would expect people using madvise()
to probably use this interface. Questions on the interface

1. What permissions would a program need to use the interface
2. Do we export both mapped and unmapped page cache. How does this
   interface gel with mincore(2)? Is there duplicate information
3. If the user already knows the file of interest, is it possible
   to list, it's cached pages without having to list all cached inodes
4. What's the size of data (expected average) and the format, binary
   or text?


-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

filecache: expose what's in the page cache

[Fengguang Wu]

[-- Attachment #1: Type: text/plain, Size: 3969 bytes --]

On Tue, Sep 25, 2007 at 01:47:42PM +0530, Balbir Singh wrote:
> Fengguang Wu wrote:
> > On Mon, Sep 24, 2007 at 05:02:02PM -0500, Matt Mackall wrote:
> >> I think Fengguang is just thinking forward to the next logical step
> >> here which is "expose what's in the page cache". Which means being
> > 
> > I have been doing it for a long time - that's the filecache patch I
> > sent you. However it's not quite ready for a public review.
> > 
> >> able to go from page back to device:inode:offset or (better, but
> >> trickier) path:offset.
> > 
> > It's doing the other way around - a top-down way.
> > 
> > First, you get a table of all cached inodes with the following fields:
> >   device-number  inode-number  file-path  cached-page-count  status
> > 
> > Then, one can query any file he's interested in, and list all its
> > cached pages in the following format:
> >   index  length  page-flags  reference-count
> 
> This design sounds good to me, I would expect people using madvise()
> to probably use this interface. Questions on the interface

Thank you, answers below. 

> 1. What permissions would a program need to use the interface

- inode list (whole system)
Only root is allowed. Or there may be leak of information.
Because we don't know the permission of the path.

- page list (for one file)
It's OK to view any file he can open.

> 2. Do we export both mapped and unmapped page cache. How does this
>    interface gel with mincore(2)? Is there duplicate information

Both are exported.
It's system wide info, and hence the superset of mincore(2).

> 3. If the user already knows the file of interest, is it possible
>    to list, it's cached pages without having to list all cached inodes

Sure, it's easy:

# echo 'cat /bin/bash' > /proc/filecache
# cat /proc/filecache

To get the inode list:

# echo 'ls' > /proc/filecache
# cat /proc/filecache

Yes, /proc/filecache accepts simple commands. Which could make it an
unfavorably complex interface... Anyway, I've been focusing on
exporting (more than enough) information. There will be a lot room of
discussion when it comes down to the details of *interface*.

> 4. What's the size of data (expected average) and the format, binary
>    or text?

Here are some numbers and output samples on my desktop:

- inode list: 185KB

#      ino       size   cached cached% refcnt state accessed   uid process         dev          file
[...]
   2888725         82       84     100      7    --      140     0 init            08:02(sda2)  /lib/libselinux.so.1
   2888724        216       84      38      7    --      140     0 init            08:02(sda2)  /lib/libsepol.so.1
   1258136         50       52     100      0    --     2349     0 init            08:02(sda2)  /etc/ld.so.cache
   2889047        115      116     100     52    --     1727     0 swapper         08:02(sda2)  /lib/ld-2.6.so
   1403527         32       32     100      1    --        1     0 swapper         08:02(sda2)  /sbin/init
[...]

- page list: bash 523B; firefox 6.5KB 

# file /bin/bash
# flags R:referenced A:active M:mmap U:uptodate D:dirty W:writeback B:buffer
# idx   len     state   refcnt
0       76      RAMU___ 2
76      4       ___U___ 1
80      5       RAMU___ 2
85      1       ___U___ 1
86      1       RAMU___ 2
87      1       RA_U___ 1
88      1       RAMU___ 2
89      4       RA_U___ 1
93      1       ___U___ 1
94      1       R__U___ 1
95      1       RA_U___ 1
96      3       RAMU___ 2
99      1       RA_U___ 1
100     1       RAMU___ 2
101     2       RA_U___ 1
103     6       RAMU___ 2
109     1       RA_U___ 1
110     10      ___U___ 1
123     10      ___U___ 1
133     4       RA_U___ 1
137     7       RAMU___ 2
144     10      ___U___ 1
154     7       RAMU___ 2
161     2       RA_U___ 1
163     1       ___U___ 1
164     2       RA_U___ 1


Attached is the patch on 2.6.23-rc6 for your convenience.
It's pretty stable and safe to use, in despite of it being a bit fat ;-)

Thank you,
Fengguang

[-- Attachment #2: filecache-2.6.23-rc6.patch --]
[-- Type: text/x-diff, Size: 31903 bytes --]

--- linux-2.6.23-rc6.orig/include/linux/mm.h
+++ linux-2.6.23-rc6/include/linux/mm.h
@@ -28,6 +28,7 @@ extern unsigned long max_mapnr;
 extern unsigned long num_physpages;
 extern void * high_memory;
 extern int page_cluster;
+extern char * const zone_names[];
 
 #ifdef CONFIG_SYSCTL
 extern int sysctl_legacy_va_layout;
--- linux-2.6.23-rc6.orig/mm/page_alloc.c
+++ linux-2.6.23-rc6/mm/page_alloc.c
@@ -87,7 +87,7 @@ int sysctl_lowmem_reserve_ratio[MAX_NR_Z
 
 EXPORT_SYMBOL(totalram_pages);
 
-static char * const zone_names[MAX_NR_ZONES] = {
+char * const zone_names[MAX_NR_ZONES] = {
 #ifdef CONFIG_ZONE_DMA
 	 "DMA",
 #endif
--- linux-2.6.23-rc6.orig/fs/dcache.c
+++ linux-2.6.23-rc6/fs/dcache.c
@@ -1810,7 +1810,10 @@ static char * __d_path( struct dentry *d
 
 		if (dentry == root && vfsmnt == rootmnt)
 			break;
-		if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
+		if (unlikely(!vfsmnt)) {
+			if (IS_ROOT(dentry))
+				break;
+		} else if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
 			/* Global root? */
 			spin_lock(&vfsmount_lock);
 			if (vfsmnt->mnt_parent == vfsmnt) {
--- linux-2.6.23-rc6.orig/include/linux/seq_file.h
+++ linux-2.6.23-rc6/include/linux/seq_file.h
@@ -32,6 +32,7 @@ struct seq_operations {
 };
 
 int seq_open(struct file *, const struct seq_operations *);
+int seq_open_private(struct file *, struct seq_operations *, void *);
 ssize_t seq_read(struct file *, char __user *, size_t, loff_t *);
 loff_t seq_lseek(struct file *, loff_t, int);
 int seq_release(struct inode *, struct file *);
--- linux-2.6.23-rc6.orig/fs/seq_file.c
+++ linux-2.6.23-rc6/fs/seq_file.c
@@ -53,6 +53,16 @@ int seq_open(struct file *file, const st
 }
 EXPORT_SYMBOL(seq_open);
 
+int seq_open_private(struct file *file, struct seq_operations *op, void *data)
+{
+	int ret = seq_open(file, op);
+
+	if (!ret)
+		((struct seq_file *)file->private_data)->private = data;
+
+	return ret;
+}
+EXPORT_SYMBOL(seq_open_private);
 /**
  *	seq_read -	->read() method for sequential files.
  *	@file: the file to read from
--- linux-2.6.23-rc6.orig/fs/nfs/client.c
+++ linux-2.6.23-rc6/fs/nfs/client.c
@@ -1188,17 +1188,7 @@ static const struct file_operations nfs_
  */
 static int nfs_server_list_open(struct inode *inode, struct file *file)
 {
-	struct seq_file *m;
-	int ret;
-
-	ret = seq_open(file, &nfs_server_list_ops);
-	if (ret < 0)
-		return ret;
-
-	m = file->private_data;
-	m->private = PDE(inode)->data;
-
-	return 0;
+	return seq_open_private(file, &nfs_server_list_ops, PDE(inode)->data);
 }
 
 /*
@@ -1258,17 +1248,7 @@ static int nfs_server_list_show(struct s
  */
 static int nfs_volume_list_open(struct inode *inode, struct file *file)
 {
-	struct seq_file *m;
-	int ret;
-
-	ret = seq_open(file, &nfs_volume_list_ops);
-	if (ret < 0)
-		return ret;
-
-	m = file->private_data;
-	m->private = PDE(inode)->data;
-
-	return 0;
+	return seq_open_private(file, &nfs_volume_list_ops, PDE(inode)->data);
 }
 
 /*
--- linux-2.6.23-rc6.orig/fs/inode.c
+++ linux-2.6.23-rc6/fs/inode.c
@@ -82,6 +82,10 @@ static struct hlist_head *inode_hashtabl
  */
 DEFINE_SPINLOCK(inode_lock);
 
+EXPORT_SYMBOL(inode_in_use);
+EXPORT_SYMBOL(inode_unused);
+EXPORT_SYMBOL(inode_lock);
+
 /*
  * iprune_mutex provides exclusion between the kswapd or try_to_free_pages
  * icache shrinking path, and the umount path.  Without this exclusion,
@@ -99,6 +103,14 @@ struct inodes_stat_t inodes_stat;
 
 static struct kmem_cache * inode_cachep __read_mostly;
 
+static inline void inode_created_by(struct inode *inode, struct task_struct *task)
+{
+#ifdef CONFIG_PROC_FILECACHE_EXTRAS
+	inode->i_cuid = task->uid;
+	memcpy(inode->i_comm, task->comm, sizeof(task->comm));
+#endif
+}
+
 static struct inode *alloc_inode(struct super_block *sb)
 {
 	static const struct address_space_operations empty_aops;
@@ -164,6 +176,7 @@ static struct inode *alloc_inode(struct 
 		}
 		inode->i_private = NULL;
 		inode->i_mapping = mapping;
+		inode_created_by(inode, current);
 	}
 	return inode;
 }
@@ -231,6 +244,8 @@ void __iget(struct inode * inode)
 	inodes_stat.nr_unused--;
 }
 
+EXPORT_SYMBOL(__iget);
+
 /**
  * clear_inode - clear an inode
  * @inode: inode to clear
--- linux-2.6.23-rc6.orig/fs/super.c
+++ linux-2.6.23-rc6/fs/super.c
@@ -47,6 +47,9 @@ struct file_system_type *get_fs_type(con
 LIST_HEAD(super_blocks);
 DEFINE_SPINLOCK(sb_lock);
 
+EXPORT_SYMBOL(super_blocks);
+EXPORT_SYMBOL(sb_lock);
+
 /**
  *	alloc_super	-	create new superblock
  *	@type:	filesystem type superblock should belong to
--- linux-2.6.23-rc6.orig/mm/vmscan.c
+++ linux-2.6.23-rc6/mm/vmscan.c
@@ -212,6 +212,7 @@ unsigned long shrink_slab(unsigned long 
 	up_read(&shrinker_rwsem);
 	return ret;
 }
+EXPORT_SYMBOL(shrink_slab);
 
 /* Called without lock on whether page is mapped, so answer is unstable */
 static inline int page_mapping_inuse(struct page *page)
--- linux-2.6.23-rc6.orig/Documentation/filesystems/proc.txt
+++ linux-2.6.23-rc6/Documentation/filesystems/proc.txt
@@ -263,6 +263,7 @@ Table 1-4: Kernel info in /proc
  driver	     Various drivers grouped here, currently rtc (2.4)
  execdomains Execdomains, related to security			(2.4)
  fb	     Frame Buffer devices				(2.4)
+ filecache   Query/drop in-memory file cache
  fs	     File system parameters, currently nfs/exports	(2.4)
  ide         Directory containing info about the IDE subsystem 
  interrupts  Interrupt usage                                   
@@ -507,6 +508,88 @@ VmallocTotal: total size of vmalloc memo
  VmallocUsed: amount of vmalloc area which is used
 VmallocChunk: largest contigious block of vmalloc area which is free
 
+..............................................................................
+
+filecache:
+
+Provides access to the in-memory file cache.
+
+To list an index of all cached files:
+
+    echo ls > /proc/filecache
+    cat /proc/filecache
+
+The output looks like:
+
+    # filecache 1.0
+    #      ino       size   cached cached%  state   refcnt  dev             file
+       1026334         91       92    100   --      66      03:02(hda2)     /lib/ld-2.3.6.so
+        233608       1242      972     78   --      66      03:02(hda2)     /lib/tls/libc-2.3.6.so
+         65203        651      476     73   --      1       03:02(hda2)     /bin/bash
+       1026445        261      160     61   --      10      03:02(hda2)     /lib/libncurses.so.5.5
+        235427         10       12    100   --      44      03:02(hda2)     /lib/tls/libdl-2.3.6.so
+
+FIELD	INTRO
+---------------------------------------------------------------------------
+ino	inode number
+size	inode size in KB
+cached	cached size in KB
+cached%	percent of file data cached
+state1	'-' clean; 'd' metadata dirty; 'D' data dirty
+state2	'-' unlocked; 'L' locked, normally indicates file being written out
+refcnt	file reference count, it's an in-kernel one, not exactly open count
+dev	major:minor numbers in hex, followed by a descriptive device name
+file	file path _inside_ the filesystem. There are several special names:
+	'(noname)':	the file name is not available
+	'(03:02)':	the file is a block device file of major:minor
+	'...(deleted)': the named file has been deleted from the disk
+
+To list the cached pages of a perticular file:
+
+    echo /bin/bash > /proc/filecache
+    cat /proc/filecache
+
+    # file /bin/bash
+    # flags R:referenced A:active U:uptodate D:dirty W:writeback M:mmap
+    # idx   len     state   refcnt
+    0       36      RAU__M  3
+    36      1       RAU__M  2
+    37      8       RAU__M  3
+    45      2       RAU___  1
+    47      6       RAU__M  3
+    53      3       RAU__M  2
+    56      2       RAU__M  3
+
+FIELD	INTRO
+----------------------------------------------------------------------------
+idx	page index
+len	number of pages which are cached and share the same state
+state	page state of the flags listed in line two
+refcnt	page reference count
+
+Careful users may notice that the file name to be queried is remembered between
+commands. Internally, the module has a global variable to store the file name
+parameter, so that it can be inherited by newly opened /proc/filecache file.
+However it can lead to interference for multiple queriers. The solution here
+is to obey a rule: only root can interactively change the file name parameter;
+normal users must go for scripts to access the interface. Scripts should do it
+by following the code example below:
+
+    filecache = open("/proc/filecache", "rw");
+    # avoid polluting the global parameter filename
+    filecache.write("set private");
+
+To instruct the kernel to drop clean caches, dentries and inodes from memory,
+causing that memory to become free:
+
+    # drop clean file data cache (i.e. file backed pagecache)
+    echo drop pagecache > /proc/filecache
+
+    # drop clean file metadata cache (i.e. dentries and inodes)
+    echo drop slabcache > /proc/filecache
+
+Note that the drop commands are non-destructive operations and dirty objects
+are not freeable, the user should run `sync' first.
 
 1.3 IDE devices in /proc/ide
 ----------------------------
--- /dev/null
+++ linux-2.6.23-rc6/fs/proc/filecache.c
@@ -0,0 +1,934 @@
+/*
+ * fs/proc/filecache.c
+ *
+ * Copyright (C) 2006, 2007 Fengguang Wu <wfg@mail.ustc.edu.cn>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/radix-tree.h>
+#include <linux/page-flags.h>
+#include <linux/pagevec.h>
+#include <linux/pagemap.h>
+#include <linux/vmalloc.h>
+#include <linux/writeback.h>
+#include <linux/buffer_head.h>
+#include <linux/parser.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/file.h>
+#include <linux/module.h>
+#include <asm/uaccess.h>
+
+/*
+ * Increase minor version when new columns are added;
+ * Increase major version when existing columns are changed.
+ */
+#define FILECACHE_VERSION	"1.0"
+
+/* Internal buffer sizes. The larger the more effcient. */
+#define SBUF_SIZE	(128<<10)
+#define IWIN_PAGE_ORDER	3
+#define IWIN_SIZE	((PAGE_SIZE<<IWIN_PAGE_ORDER) / sizeof(struct inode *))
+
+/*
+ * Session management.
+ *
+ * Each opened /proc/filecache file is assiocated with a session object.
+ * Also there is a global_session that maintains status across open()/close()
+ * (i.e. the lifetime of an opened file), so that a casual user can query the
+ * filecache via _multiple_ simple shell commands like
+ * 'echo cat /bin/bash > /proc/filecache; cat /proc/filecache'.
+ *
+ * session.query_file is the file whose cache info is to be queried.
+ * Its value determines what we get on read():
+ * 	- NULL: ii_*() called to show the inode index
+ * 	- filp: pg_*() called to show the page groups of a filp
+ *
+ * session.query_file is
+ * 	- cloned from global_session.query_file on open();
+ * 	- updated on write("cat filename");
+ * 	  note that the new file will also be saved in global_session.query_file if
+ * 	  session.private_session is false.
+ */
+
+struct session {
+	/* options */
+	int		private_session;
+	unsigned long	ls_options;
+	dev_t		ls_dev;
+
+	/* parameters */
+	struct file	*query_file;
+
+	/* seqfile pos */
+	pgoff_t		start_offset;
+	pgoff_t		next_offset;
+
+	/* inode at last pos */
+	struct {
+		unsigned long pos;
+		unsigned long state;
+		struct inode *inode;
+		struct inode *pinned_inode;
+	} ipos;
+
+	/* inode window */
+	struct {
+		unsigned long cursor;
+		unsigned long origin;
+		unsigned long size;
+		struct inode **inodes;
+	} iwin;
+};
+
+static struct session global_session;
+
+/*
+ * Session address is stored in proc_file->f_ra.start:
+ * we assume that there will be no readahead for proc_file.
+ */
+static struct session *get_session(struct file *proc_file)
+{
+	return (struct session *)proc_file->f_ra.start;
+}
+
+static void set_session(struct file *proc_file, struct session *s)
+{
+	BUG_ON(proc_file->f_ra.start);
+	proc_file->f_ra.start = (unsigned long)s;
+}
+
+static void update_global_file(struct session *s)
+{
+	if (s->private_session)
+		return;
+
+	if (global_session.query_file)
+		fput(global_session.query_file);
+
+	global_session.query_file = s->query_file;
+
+	if (global_session.query_file)
+		get_file(global_session.query_file);
+}
+
+/*
+ * Cases of the name:
+ * 1) NULL                (new session)
+ * 	s->query_file = global_session.query_file = 0;
+ * 2) ""                  (ls/la)
+ * 	s->query_file = global_session.query_file;
+ * 3) a regular file name (cat newfile)
+ * 	s->query_file = global_session.query_file = newfile;
+ */
+static int session_update_file(struct session *s, char *name)
+{
+	static DEFINE_MUTEX(mutex); /* protects global_session.query_file */
+	int err = 0;
+
+	mutex_lock(&mutex);
+
+	/*
+	 * We are to quit, or to list the cached files.
+	 * Reset *.query_file.
+	 */
+	if (!name) {
+		if (s->query_file) {
+			fput(s->query_file);
+			s->query_file = NULL;
+		}
+		update_global_file(s);
+		goto out;
+	}
+
+	/*
+	 * This is a new session.
+	 * Inherit options/parameters from global ones.
+	 */
+	if (name[0] == '\0') {
+		*s = global_session;
+		if (s->query_file)
+			get_file(s->query_file);
+		goto out;
+	}
+
+	/*
+	 * Open the named file.
+	 */
+	if (s->query_file)
+		fput(s->query_file);
+	s->query_file = filp_open(name, O_RDONLY|O_LARGEFILE, 0);
+	if (IS_ERR(s->query_file)) {
+		err = PTR_ERR(s->query_file);
+		s->query_file = NULL;
+	} else
+		update_global_file(s);
+
+out:
+	mutex_unlock(&mutex);
+
+	return err;
+}
+
+static struct session *session_create(void)
+{
+	struct session *s;
+	int err = 0;
+
+	s = kmalloc(sizeof(*s), GFP_KERNEL);
+	if (s)
+		err = session_update_file(s, "");
+	else
+		err = -ENOMEM;
+
+	return err ? ERR_PTR(err) : s;
+}
+
+static void session_release(struct session *s)
+{
+	if (s->ipos.pinned_inode)
+		iput(s->ipos.pinned_inode);
+	if (s->query_file)
+		fput(s->query_file);
+	kfree(s);
+}
+
+
+/*
+ * Listing of cached files.
+ *
+ * Usage:
+ * 		echo > /proc/filecache  # enter listing mode
+ * 		cat /proc/filecache     # get the file listing
+ */
+
+/* code style borrowed from ib_srp.c */
+enum {
+	LS_OPT_ERR	=	0,
+	LS_OPT_NOCLEAN	=	1 << 0,
+	LS_OPT_NODIRTY	=	1 << 1,
+	LS_OPT_NOUNUSED	=	1 << 2,
+	LS_OPT_EMPTY	=	1 << 3,
+	LS_OPT_ALL	=	1 << 4,
+	LS_OPT_DEV	=	1 << 5,
+};
+
+static match_table_t ls_opt_tokens = {
+	{ LS_OPT_NOCLEAN,	"noclean" 	},
+	{ LS_OPT_NODIRTY,	"nodirty" 	},
+	{ LS_OPT_NOUNUSED,	"nounused" 	},
+	{ LS_OPT_EMPTY,		"empty"		},
+	{ LS_OPT_ALL,		"all" 		},
+	{ LS_OPT_DEV,		"dev=%s"	},
+	{ LS_OPT_ERR,		NULL 		}
+};
+
+static int ls_parse_options(const char *buf, struct session *s)
+{
+	substring_t args[MAX_OPT_ARGS];
+	char *options, *sep_opt;
+	char *p;
+	int token;
+	int ret = 0;
+
+	if (!buf)
+		return 0;
+	options = kstrdup(buf, GFP_KERNEL);
+	if (!options)
+		return -ENOMEM;
+
+	s->ls_options = 0;
+	sep_opt = options;
+	while ((p = strsep(&sep_opt, " ")) != NULL) {
+		if (!*p)
+			continue;
+
+		token = match_token(p, ls_opt_tokens, args);
+
+		switch (token) {
+		case LS_OPT_NOCLEAN:
+		case LS_OPT_NODIRTY:
+		case LS_OPT_NOUNUSED:
+		case LS_OPT_EMPTY:
+		case LS_OPT_ALL:
+			s->ls_options |= token;
+			break;
+		case LS_OPT_DEV:
+			p = match_strdup(args);
+			if (!p) {
+				ret = -ENOMEM;
+				goto out;
+			}
+			if (*p == '/') {
+				struct kstat stat;
+				struct nameidata nd;
+				ret = path_lookup(p, LOOKUP_FOLLOW, &nd);
+				if (!ret)
+					ret = vfs_getattr(nd.mnt,
+							  nd.dentry, &stat);
+				if (!ret)
+					s->ls_dev = stat.rdev;
+			} else
+				s->ls_dev = simple_strtoul(p, NULL, 0);
+			/* printk("%lx %s\n", (long)s->ls_dev, p); */
+			kfree(p);
+			break;
+
+		default:
+			printk(KERN_WARNING "unknown parameter or missing value "
+			       "'%s' in ls command\n", p);
+			ret = -EINVAL;
+			goto out;
+		}
+	}
+
+out:
+	kfree(options);
+	return ret;
+}
+
+/*
+ * Add possible filters here.
+ * No permission check: we cannot verify the path's permission anyway.
+ * We simply demand root previledge for accessing /proc/filecache.
+ */
+static int may_show_inode(struct session *s, struct inode *inode)
+{
+	if (!atomic_read(&inode->i_count))
+		return 0;
+	if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE))
+		return 0;
+	if (!inode->i_mapping)
+		return 0;
+
+	if (s->ls_dev && s->ls_dev != inode->i_sb->s_dev)
+		return 0;
+
+	if (s->ls_options & LS_OPT_ALL)
+		return 1;
+
+	if (!(s->ls_options & LS_OPT_EMPTY) && !inode->i_mapping->nrpages)
+		return 0;
+
+	if ((s->ls_options & LS_OPT_NOCLEAN) && !(inode->i_state & I_DIRTY))
+		return 0;
+
+	if ((s->ls_options & LS_OPT_NODIRTY) && (inode->i_state & I_DIRTY))
+		return 0;
+
+	if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
+	      S_ISLNK(inode->i_mode) || S_ISBLK(inode->i_mode)))
+		return 0;
+
+	return 1;
+}
+
+/*
+ * Full: there are more data following.
+ */
+static int iwin_full(struct session *s)
+{
+	return !s->iwin.cursor ||
+		s->iwin.cursor > s->iwin.origin + s->iwin.size;
+}
+
+static int iwin_push(struct session *s, struct inode *inode)
+{
+	if (!may_show_inode(s, inode))
+		return 0;
+
+	s->iwin.cursor++;
+
+	if (s->iwin.size >= IWIN_SIZE)
+		return 1;
+
+	if (s->iwin.cursor > s->iwin.origin)
+		s->iwin.inodes[s->iwin.size++] = inode;
+	return 0;
+}
+
+/*
+ * Travease the inode lists in order - newest first.
+ * And fill @s->iwin.inodes with inodes positioned in [@pos, @pos+IWIN_SIZE).
+ */
+static int iwin_fill(struct session *s, unsigned long pos)
+{
+	struct inode *inode;
+	struct super_block *sb;
+
+	s->iwin.origin = pos;
+	s->iwin.cursor = 0;
+	s->iwin.size = 0;
+
+	/*
+	 * We have a cursor inode, clean and expected to be unchanged.
+	 */
+	if (s->ipos.inode && pos >= s->ipos.pos &&
+			!(s->ipos.state & I_DIRTY) &&
+			s->ipos.state == s->ipos.inode->i_state) {
+		inode = s->ipos.inode;
+		s->iwin.cursor = s->ipos.pos;
+		goto continue_from_saved;
+	}
+
+	if (s->ls_options & LS_OPT_NODIRTY)
+		goto clean_inodes;
+
+	spin_lock(&sb_lock);
+	list_for_each_entry(sb, &super_blocks, s_list) {
+		if (s->ls_dev && s->ls_dev != sb->s_dev)
+			continue;
+
+		list_for_each_entry(inode, &sb->s_dirty, i_list) {
+			if (iwin_push(s, inode))
+				goto out_full_unlock;
+		}
+		list_for_each_entry(inode, &sb->s_io, i_list) {
+			if (iwin_push(s, inode))
+				goto out_full_unlock;
+		}
+	}
+	spin_unlock(&sb_lock);
+
+clean_inodes:
+	list_for_each_entry(inode, &inode_in_use, i_list) {
+		if (iwin_push(s, inode))
+			goto out_full;
+continue_from_saved:
+		;
+	}
+
+	if (s->ls_options & LS_OPT_NOUNUSED)
+		return 0;
+
+	list_for_each_entry(inode, &inode_unused, i_list) {
+		if (iwin_push(s, inode))
+			goto out_full;
+	}
+
+	return 0;
+
+out_full_unlock:
+	spin_unlock(&sb_lock);
+out_full:
+	return 1;
+}
+
+static struct inode *iwin_inode(struct session *s, unsigned long pos)
+{
+	if ((iwin_full(s) && pos >= s->iwin.origin + s->iwin.size)
+			  || pos < s->iwin.origin)
+		iwin_fill(s, pos);
+
+	if (pos >= s->iwin.cursor)
+		return NULL;
+
+	s->ipos.pos = pos;
+	s->ipos.inode = s->iwin.inodes[pos - s->iwin.origin];
+	BUG_ON(!s->ipos.inode);
+	return s->ipos.inode;
+}
+
+static void show_inode(struct seq_file *m, struct inode *inode)
+{
+	char state[] = "--"; /* dirty, locked */
+	struct dentry *dentry;
+	loff_t size = i_size_read(inode);
+	unsigned long nrpages;
+	int percent;
+	int refcnt;
+	int shift;
+
+	if (!size)
+		size++;
+
+	if (inode->i_mapping)
+		nrpages = inode->i_mapping->nrpages;
+	else {
+		nrpages = 0;
+		WARN_ON(1);
+	}
+
+	for (shift = 0; (size >> shift) > ULONG_MAX / 128; shift += 12)
+		;
+	percent = min(100UL, (((100 * nrpages) >> shift) << PAGE_CACHE_SHIFT) /
+						(unsigned long)(size >> shift));
+
+	if (inode->i_state & (I_DIRTY_DATASYNC|I_DIRTY_PAGES))
+		state[0] = 'D';
+	else if (inode->i_state & I_DIRTY_SYNC)
+		state[0] = 'd';
+
+	if (inode->i_state & I_LOCK)
+		state[0] = 'L';
+
+	refcnt = 0;
+	list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
+		refcnt += atomic_read(&dentry->d_count);
+	}
+
+	seq_printf(m, "%10lu %10llu %8lu %7d ",
+			inode->i_ino,
+			DIV_ROUND_UP(size, 1024),
+			nrpages << (PAGE_CACHE_SHIFT - 10),
+			percent);
+
+	seq_printf(m, "%6d %5s ",
+			refcnt,
+			state);
+
+#ifdef CONFIG_PROC_FILECACHE_EXTRAS
+	seq_printf(m, "%8u %5u %-16s",
+			inode->i_access_count,
+			inode->i_cuid,
+			inode->i_comm);
+#endif
+
+	seq_printf(m, "%02x:%02x(%s)\t",
+			MAJOR(inode->i_sb->s_dev),
+			MINOR(inode->i_sb->s_dev),
+			inode->i_sb->s_id);
+
+	if (list_empty(&inode->i_dentry)) {
+		if (!atomic_read(&inode->i_count))
+			seq_puts(m, "(noname)\n");
+		else
+			seq_printf(m, "(%02x:%02x)\n",
+					imajor(inode), iminor(inode));
+	} else {
+		dentry = list_entry(inode->i_dentry.next,
+							struct dentry, d_alias);
+		seq_path(m, NULL, dentry, " \t\n\\");
+		seq_putc(m, '\n');
+	}
+}
+
+static int ii_show(struct seq_file *m, void *v)
+{
+	unsigned long index = *(loff_t *) v;
+	struct session *s = m->private;
+        struct inode *inode;
+
+	if (index == 0) {
+		seq_puts(m, "# filecache " FILECACHE_VERSION "\n");
+		seq_puts(m, "#      ino       size   cached cached% "
+				"refcnt state "
+#ifdef CONFIG_PROC_FILECACHE_EXTRAS
+				"accessed   uid process         "
+#endif
+				"dev\t\tfile\n");
+	}
+
+        inode = iwin_inode(s,index);
+	show_inode(m, inode);
+
+	return 0;
+}
+
+static void *ii_start(struct seq_file *m, loff_t *pos)
+{
+	struct session *s = m->private;
+
+	s->iwin.size = 0;
+	s->iwin.inodes = (struct inode **)
+				__get_free_pages( GFP_KERNEL, IWIN_PAGE_ORDER);
+	if (!s->iwin.inodes)
+		return NULL;
+
+	spin_lock(&inode_lock);
+
+	return iwin_inode(s, *pos) ? pos : NULL;
+}
+
+static void *ii_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	struct session *s = m->private;
+
+	(*pos)++;
+	return iwin_inode(s, *pos) ? pos : NULL;
+}
+
+static void ii_stop(struct seq_file *m, void *v)
+{
+	struct session *s = m->private;
+	struct inode *inode = s->ipos.inode;
+
+	if (!s->iwin.inodes)
+		return;
+
+	if (inode) {
+		__iget(inode);
+		s->ipos.state = inode->i_state;
+	}
+	spin_unlock(&inode_lock);
+
+	free_pages((unsigned long) s->iwin.inodes, IWIN_PAGE_ORDER);
+	if (s->ipos.pinned_inode)
+		iput(s->ipos.pinned_inode);
+	s->ipos.pinned_inode = inode;
+}
+
+/*
+ * Listing of cached page ranges of a file.
+ *
+ * Usage:
+ * 		echo 'file name' > /proc/filecache
+ * 		cat /proc/filecache
+ */
+
+unsigned long page_mask;
+#define PG_MMAP		PG_lru		/* reuse any non-relevant flag */
+#define PG_BUFFER	PG_readahead	/* ditto */
+
+/*
+ * Page state names, prefixed by their abbreviations.
+ */
+struct {
+	unsigned long	mask;
+	const char     *name;
+	int		faked;
+} page_flag [] = {
+	{1 << PG_referenced,	"R:referenced",	0},
+	{1 << PG_active,	"A:active",	0},
+	{1 << PG_MMAP,		"M:mmap",	1},
+
+	{1 << PG_uptodate,	"U:uptodate",	0},
+	{1 << PG_dirty,		"D:dirty",	0},
+	{1 << PG_writeback,	"W:writeback",	0},
+
+	{1 << PG_BUFFER,	"B:buffer",	1},
+
+};
+
+static unsigned long page_flags(struct page* page)
+{
+	unsigned long flags;
+
+	flags = page->flags & page_mask;
+
+	if (page_mapped(page))
+		flags |= (1 << PG_MMAP);
+
+	if (page_has_buffers(page))
+		flags |= (1 << PG_BUFFER);
+
+	return flags;
+}
+
+static int pages_similiar(struct page* page0, struct page* page)
+{
+	if (page_count(page0) != page_count(page))
+		return 0;
+
+	if (page_flags(page0) != page_flags(page))
+		return 0;
+
+	return 1;
+}
+
+static void show_range(struct seq_file *m, struct page* page, unsigned long len)
+{
+	int i;
+	unsigned long flags;
+
+	if (!m || !page)
+		return;
+
+	seq_printf(m, "%lu\t%lu\t", page->index, len);
+
+	flags = page_flags(page);
+	for (i = 0; i < ARRAY_SIZE(page_flag); i++)
+		seq_putc(m, (flags & page_flag[i].mask) ?
+					page_flag[i].name[0] : '_');
+
+	seq_printf(m, "\t%d\n", page_count(page));
+}
+
+#define BATCH_LINES	100
+static pgoff_t show_file_cache(struct seq_file *m,
+				struct address_space *mapping, pgoff_t start)
+{
+	int i;
+	int lines = 0;
+	pgoff_t len = 0;
+	struct pagevec pvec;
+	struct page *page;
+	struct page *page0 = NULL;
+
+	for (;;) {
+		pagevec_init(&pvec, 0);
+		pvec.nr = radix_tree_gang_lookup(&mapping->page_tree,
+				(void **)pvec.pages, start + len, PAGEVEC_SIZE);
+
+		if (pvec.nr == 0) {
+			show_range(m, page0, len);
+			start = ULONG_MAX;
+			goto out;
+		}
+
+		if (!page0)
+			page0 = pvec.pages[0];
+
+		for (i = 0; i < pvec.nr; i++) {
+			page = pvec.pages[i];
+
+			if (page->index == start + len &&
+					pages_similiar(page0, page))
+				len++;
+			else {
+				show_range(m, page0, len);
+				page0 = page;
+				start = page->index;
+				len = 1;
+				if (++lines > BATCH_LINES)
+					goto out;
+			}
+		}
+	}
+
+out:
+	return start;
+}
+
+static int pg_show(struct seq_file *m, void *v)
+{
+	struct session *s = m->private;
+	struct file *file = s->query_file;
+	pgoff_t offset;
+
+	if (!file)
+		return ii_show(m, v);
+
+	offset = *(loff_t *) v;
+
+	if (!offset) { /* print header */
+		int i;
+
+		seq_puts(m, "# file ");
+		seq_path(m, file->f_vfsmnt, file->f_dentry, " \t\n\\");
+
+		seq_puts(m, "\n# flags");
+		for (i = 0; i < ARRAY_SIZE(page_flag); i++)
+			seq_printf(m, " %s", page_flag[i].name);
+
+		seq_puts(m, "\n# idx\tlen\tstate\trefcnt\n");
+	}
+
+	s->start_offset = offset;
+	s->next_offset = show_file_cache(m, file->f_mapping, offset);
+
+	return 0;
+}
+
+static void *file_pos(struct file *file, loff_t *pos)
+{
+	loff_t size = i_size_read(file->f_mapping->host);
+	pgoff_t end = DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
+	pgoff_t offset = *pos;
+
+	return offset < end ? pos : NULL;
+}
+
+static void *pg_start(struct seq_file *m, loff_t *pos)
+{
+	struct session *s = m->private;
+	struct file *file = s->query_file;
+	pgoff_t offset = *pos;
+
+	if (!file)
+		return ii_start(m, pos);
+
+	read_lock_irq(&file->f_mapping->tree_lock);
+
+	if (offset - s->start_offset == 1)
+		*pos = s->next_offset;
+	return file_pos(file, pos);
+}
+
+static void *pg_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	struct session *s = m->private;
+	struct file *file = s->query_file;
+
+	if (!file)
+		return ii_next(m, v, pos);
+
+	*pos = s->next_offset;
+	return file_pos(file, pos);
+}
+
+static void pg_stop(struct seq_file *m, void *v)
+{
+	struct session *s = m->private;
+	struct file *file = s->query_file;
+
+	if (!file)
+		return ii_stop(m, v);
+
+	read_unlock_irq(&file->f_mapping->tree_lock);
+}
+
+struct seq_operations seq_filecache_op = {
+	.start	= pg_start,
+	.next	= pg_next,
+	.stop	= pg_stop,
+	.show	= pg_show,
+};
+
+
+/*
+ * Proc file operations.
+ */
+
+static int filecache_open(struct inode *inode, struct file *proc_file)
+{
+	struct seq_file *m;
+	struct session *s;
+	unsigned size;
+	char *buf = 0;
+	int ret;
+
+	if (!try_module_get(THIS_MODULE))
+		return -ENOENT;
+
+	s = session_create();
+	if (IS_ERR(s)) {
+		ret = PTR_ERR(s);
+		goto out;
+	}
+	set_session(proc_file, s);
+
+	size = SBUF_SIZE;
+	buf = kmalloc(size, GFP_KERNEL);
+	if (!buf) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	ret = seq_open(proc_file, &seq_filecache_op);
+	if (!ret) {
+		m = proc_file->private_data;
+		m->private = s;
+		m->buf = buf;
+		m->size = size;
+	}
+
+out:
+	if (ret) {
+		kfree(s);
+		kfree(buf);
+		module_put(THIS_MODULE);
+	}
+	return ret;
+}
+
+static int filecache_release(struct inode *inode, struct file *proc_file)
+{
+	struct session *s = get_session(proc_file);
+	int ret;
+
+	session_release(s);
+	ret = seq_release(inode, proc_file);
+	module_put(THIS_MODULE);
+	return ret;
+}
+
+ssize_t filecache_write(struct file *proc_file, const char __user * buffer,
+			size_t count, loff_t *ppos)
+{
+	struct session *s;
+	char *name;
+	int err = 0;
+
+	if (count >= PATH_MAX + 5)
+		return -ENAMETOOLONG;
+
+	name = kmalloc(count+1, GFP_KERNEL);
+	if (!name)
+		return -ENOMEM;
+
+	if (copy_from_user(name, buffer, count)) {
+		err = -EFAULT;
+		goto out;
+	}
+
+	/* strip the optional newline */
+	if (count && name[count-1] == '\n')
+		name[count-1] = '\0';
+	else
+		name[count] = '\0';
+
+	s = get_session(proc_file);
+	if (!strcmp(name, "set private")) {
+		s->private_session = 1;
+		goto out;
+	}
+
+	if (!strncmp(name, "cat ", 4)) {
+		err = session_update_file(s, name+4);
+		goto out;
+	}
+
+	if (!strncmp(name, "ls", 2)) {
+		err = session_update_file(s, NULL);
+		if (!err)
+			err = ls_parse_options(name+2, s);
+		if (!err && !s->private_session) {
+			global_session.ls_dev = s->ls_dev;
+			global_session.ls_options = s->ls_options;
+		}
+		goto out;
+	}
+
+	/* err = -EINVAL; */
+	err = session_update_file(s, name);
+
+out:
+	kfree(name);
+
+	return err ? err : count;
+}
+
+static struct file_operations proc_filecache_fops = {
+	.owner		= THIS_MODULE,
+	.open		= filecache_open,
+	.release	= filecache_release,
+	.write		= filecache_write,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+};
+
+
+static __init int filecache_init(void)
+{
+	int i;
+	struct proc_dir_entry *entry;
+
+	entry = create_proc_entry("filecache", 0600, NULL);
+	if (entry)
+		entry->proc_fops = &proc_filecache_fops;
+
+	for (page_mask = i = 0; i < ARRAY_SIZE(page_flag); i++)
+		if (!page_flag[i].faked)
+			page_mask |= page_flag[i].mask;
+
+	return 0;
+}
+
+static void filecache_exit(void)
+{
+	remove_proc_entry("filecache", NULL);
+	if (global_session.query_file)
+		fput(global_session.query_file);
+}
+
+MODULE_AUTHOR("Fengguang Wu <wfg@mail.ustc.edu.cn>");
+MODULE_LICENSE("GPL");
+
+module_init(filecache_init);
+module_exit(filecache_exit);
--- linux-2.6.23-rc6.orig/include/linux/fs.h
+++ linux-2.6.23-rc6/include/linux/fs.h
@@ -595,6 +595,12 @@ struct inode {
 	void			*i_security;
 #endif
 	void			*i_private; /* fs or device private pointer */
+
+#ifdef CONFIG_PROC_FILECACHE_EXTRAS
+	unsigned int		i_access_count;	/* opened how many times? */
+	uid_t			i_cuid;		/* opened first by which user? */
+	char			i_comm[16];	/* opened first by which app? */
+#endif
 };
 
 /*
@@ -683,6 +689,13 @@ static inline unsigned imajor(const stru
 	return MAJOR(inode->i_rdev);
 }
 
+static inline void inode_accessed(struct inode *inode)
+{
+#ifdef CONFIG_PROC_FILECACHE_EXTRAS
+	inode->i_access_count++;
+#endif
+}
+
 extern struct block_device *I_BDEV(struct inode *inode);
 
 struct fown_struct {
--- linux-2.6.23-rc6.orig/fs/open.c
+++ linux-2.6.23-rc6/fs/open.c
@@ -765,6 +765,7 @@ static struct file *__dentry_open(struct
 			goto cleanup_all;
 	}
 
+	inode_accessed(inode);
 	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 
 	file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
--- linux-2.6.23-rc6.orig/fs/Kconfig
+++ linux-2.6.23-rc6/fs/Kconfig
@@ -1028,6 +1028,36 @@ config CONFIGFS_FS
 	  Both sysfs and configfs can and should exist together on the
 	  same system. One is not a replacement for the other.
 
+config PROC_FILECACHE
+	tristate "/proc/filecache support"
+	default m
+	depends on PROC_FS
+	help
+	  This option creates a file /proc/filecache which enables one to
+	  query/drop the cached files in memory.
+
+	  A quick start guide:
+
+	  # echo 'ls' > /proc/filecache
+	  # head /proc/filecache
+
+	  # echo 'cat /bin/bash' > /proc/filecache
+	  # head /proc/filecache
+
+	  # echo 'drop pagecache' > /proc/filecache
+	  # echo 'drop slabcache' > /proc/filecache
+
+	  For more details, please check Documentation/filesystems/proc.txt .
+
+	  It can be a handy tool for sysadms and desktop users.
+
+config PROC_FILECACHE_EXTRAS
+	bool "track extra states"
+	default y
+	depends on PROC_FILECACHE
+	help
+	  Track extra states that costs a little more time/space.
+
 endmenu
 
 menu "Miscellaneous filesystems"
--- linux-2.6.23-rc6.orig/fs/proc/Makefile
+++ linux-2.6.23-rc6/fs/proc/Makefile
@@ -2,7 +2,8 @@
 # Makefile for the Linux proc filesystem routines.
 #
 
-obj-$(CONFIG_PROC_FS) += proc.o
+obj-$(CONFIG_PROC_FS)		+= proc.o
+obj-$(CONFIG_PROC_FILECACHE)	+= filecache.o
 
 proc-y			:= nommu.o task_nommu.o
 proc-$(CONFIG_MMU)	:= mmu.o task_mmu.o

filecache: expose what's in the page cache

[Fengguang Wu]

[-- Attachment #1: Type: text/plain, Size: 3969 bytes --]

On Tue, Sep 25, 2007 at 01:47:42PM +0530, Balbir Singh wrote:
> Fengguang Wu wrote:
> > On Mon, Sep 24, 2007 at 05:02:02PM -0500, Matt Mackall wrote:
> >> I think Fengguang is just thinking forward to the next logical step
> >> here which is "expose what's in the page cache". Which means being
> > 
> > I have been doing it for a long time - that's the filecache patch I
> > sent you. However it's not quite ready for a public review.
> > 
> >> able to go from page back to device:inode:offset or (better, but
> >> trickier) path:offset.
> > 
> > It's doing the other way around - a top-down way.
> > 
> > First, you get a table of all cached inodes with the following fields:
> >   device-number  inode-number  file-path  cached-page-count  status
> > 
> > Then, one can query any file he's interested in, and list all its
> > cached pages in the following format:
> >   index  length  page-flags  reference-count
> 
> This design sounds good to me, I would expect people using madvise()
> to probably use this interface. Questions on the interface

Thank you, answers below. 

> 1. What permissions would a program need to use the interface

- inode list (whole system)
Only root is allowed. Or there may be leak of information.
Because we don't know the permission of the path.

- page list (for one file)
It's OK to view any file he can open.

> 2. Do we export both mapped and unmapped page cache. How does this
>    interface gel with mincore(2)? Is there duplicate information

Both are exported.
It's system wide info, and hence the superset of mincore(2).

> 3. If the user already knows the file of interest, is it possible
>    to list, it's cached pages without having to list all cached inodes

Sure, it's easy:

# echo 'cat /bin/bash' > /proc/filecache
# cat /proc/filecache

To get the inode list:

# echo 'ls' > /proc/filecache
# cat /proc/filecache

Yes, /proc/filecache accepts simple commands. Which could make it an
unfavorably complex interface... Anyway, I've been focusing on
exporting (more than enough) information. There will be a lot room of
discussion when it comes down to the details of *interface*.

> 4. What's the size of data (expected average) and the format, binary
>    or text?

Here are some numbers and output samples on my desktop:

- inode list: 185KB

#      ino       size   cached cached% refcnt state accessed   uid process         dev          file
[...]
   2888725         82       84     100      7    --      140     0 init            08:02(sda2)  /lib/libselinux.so.1
   2888724        216       84      38      7    --      140     0 init            08:02(sda2)  /lib/libsepol.so.1
   1258136         50       52     100      0    --     2349     0 init            08:02(sda2)  /etc/ld.so.cache
   2889047        115      116     100     52    --     1727     0 swapper         08:02(sda2)  /lib/ld-2.6.so
   1403527         32       32     100      1    --        1     0 swapper         08:02(sda2)  /sbin/init
[...]

- page list: bash 523B; firefox 6.5KB 

# file /bin/bash
# flags R:referenced A:active M:mmap U:uptodate D:dirty W:writeback B:buffer
# idx   len     state   refcnt
0       76      RAMU___ 2
76      4       ___U___ 1
80      5       RAMU___ 2
85      1       ___U___ 1
86      1       RAMU___ 2
87      1       RA_U___ 1
88      1       RAMU___ 2
89      4       RA_U___ 1
93      1       ___U___ 1
94      1       R__U___ 1
95      1       RA_U___ 1
96      3       RAMU___ 2
99      1       RA_U___ 1
100     1       RAMU___ 2
101     2       RA_U___ 1
103     6       RAMU___ 2
109     1       RA_U___ 1
110     10      ___U___ 1
123     10      ___U___ 1
133     4       RA_U___ 1
137     7       RAMU___ 2
144     10      ___U___ 1
154     7       RAMU___ 2
161     2       RA_U___ 1
163     1       ___U___ 1
164     2       RA_U___ 1


Attached is the patch on 2.6.23-rc6 for your convenience.
It's pretty stable and safe to use, in despite of it being a bit fat ;-)

Thank you,
Fengguang

[-- Attachment #2: filecache-2.6.23-rc6.patch --]
[-- Type: text/x-diff, Size: 31903 bytes --]

--- linux-2.6.23-rc6.orig/include/linux/mm.h
+++ linux-2.6.23-rc6/include/linux/mm.h
@@ -28,6 +28,7 @@ extern unsigned long max_mapnr;
 extern unsigned long num_physpages;
 extern void * high_memory;
 extern int page_cluster;
+extern char * const zone_names[];
 
 #ifdef CONFIG_SYSCTL
 extern int sysctl_legacy_va_layout;
--- linux-2.6.23-rc6.orig/mm/page_alloc.c
+++ linux-2.6.23-rc6/mm/page_alloc.c
@@ -87,7 +87,7 @@ int sysctl_lowmem_reserve_ratio[MAX_NR_Z
 
 EXPORT_SYMBOL(totalram_pages);
 
-static char * const zone_names[MAX_NR_ZONES] = {
+char * const zone_names[MAX_NR_ZONES] = {
 #ifdef CONFIG_ZONE_DMA
 	 "DMA",
 #endif
--- linux-2.6.23-rc6.orig/fs/dcache.c
+++ linux-2.6.23-rc6/fs/dcache.c
@@ -1810,7 +1810,10 @@ static char * __d_path( struct dentry *d
 
 		if (dentry == root && vfsmnt == rootmnt)
 			break;
-		if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
+		if (unlikely(!vfsmnt)) {
+			if (IS_ROOT(dentry))
+				break;
+		} else if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
 			/* Global root? */
 			spin_lock(&vfsmount_lock);
 			if (vfsmnt->mnt_parent == vfsmnt) {
--- linux-2.6.23-rc6.orig/include/linux/seq_file.h
+++ linux-2.6.23-rc6/include/linux/seq_file.h
@@ -32,6 +32,7 @@ struct seq_operations {
 };
 
 int seq_open(struct file *, const struct seq_operations *);
+int seq_open_private(struct file *, struct seq_operations *, void *);
 ssize_t seq_read(struct file *, char __user *, size_t, loff_t *);
 loff_t seq_lseek(struct file *, loff_t, int);
 int seq_release(struct inode *, struct file *);
--- linux-2.6.23-rc6.orig/fs/seq_file.c
+++ linux-2.6.23-rc6/fs/seq_file.c
@@ -53,6 +53,16 @@ int seq_open(struct file *file, const st
 }
 EXPORT_SYMBOL(seq_open);
 
+int seq_open_private(struct file *file, struct seq_operations *op, void *data)
+{
+	int ret = seq_open(file, op);
+
+	if (!ret)
+		((struct seq_file *)file->private_data)->private = data;
+
+	return ret;
+}
+EXPORT_SYMBOL(seq_open_private);
 /**
  *	seq_read -	->read() method for sequential files.
  *	@file: the file to read from
--- linux-2.6.23-rc6.orig/fs/nfs/client.c
+++ linux-2.6.23-rc6/fs/nfs/client.c
@@ -1188,17 +1188,7 @@ static const struct file_operations nfs_
  */
 static int nfs_server_list_open(struct inode *inode, struct file *file)
 {
-	struct seq_file *m;
-	int ret;
-
-	ret = seq_open(file, &nfs_server_list_ops);
-	if (ret < 0)
-		return ret;
-
-	m = file->private_data;
-	m->private = PDE(inode)->data;
-
-	return 0;
+	return seq_open_private(file, &nfs_server_list_ops, PDE(inode)->data);
 }
 
 /*
@@ -1258,17 +1248,7 @@ static int nfs_server_list_show(struct s
  */
 static int nfs_volume_list_open(struct inode *inode, struct file *file)
 {
-	struct seq_file *m;
-	int ret;
-
-	ret = seq_open(file, &nfs_volume_list_ops);
-	if (ret < 0)
-		return ret;
-
-	m = file->private_data;
-	m->private = PDE(inode)->data;
-
-	return 0;
+	return seq_open_private(file, &nfs_volume_list_ops, PDE(inode)->data);
 }
 
 /*
--- linux-2.6.23-rc6.orig/fs/inode.c
+++ linux-2.6.23-rc6/fs/inode.c
@@ -82,6 +82,10 @@ static struct hlist_head *inode_hashtabl
  */
 DEFINE_SPINLOCK(inode_lock);
 
+EXPORT_SYMBOL(inode_in_use);
+EXPORT_SYMBOL(inode_unused);
+EXPORT_SYMBOL(inode_lock);
+
 /*
  * iprune_mutex provides exclusion between the kswapd or try_to_free_pages
  * icache shrinking path, and the umount path.  Without this exclusion,
@@ -99,6 +103,14 @@ struct inodes_stat_t inodes_stat;
 
 static struct kmem_cache * inode_cachep __read_mostly;
 
+static inline void inode_created_by(struct inode *inode, struct task_struct *task)
+{
+#ifdef CONFIG_PROC_FILECACHE_EXTRAS
+	inode->i_cuid = task->uid;
+	memcpy(inode->i_comm, task->comm, sizeof(task->comm));
+#endif
+}
+
 static struct inode *alloc_inode(struct super_block *sb)
 {
 	static const struct address_space_operations empty_aops;
@@ -164,6 +176,7 @@ static struct inode *alloc_inode(struct 
 		}
 		inode->i_private = NULL;
 		inode->i_mapping = mapping;
+		inode_created_by(inode, current);
 	}
 	return inode;
 }
@@ -231,6 +244,8 @@ void __iget(struct inode * inode)
 	inodes_stat.nr_unused--;
 }
 
+EXPORT_SYMBOL(__iget);
+
 /**
  * clear_inode - clear an inode
  * @inode: inode to clear
--- linux-2.6.23-rc6.orig/fs/super.c
+++ linux-2.6.23-rc6/fs/super.c
@@ -47,6 +47,9 @@ struct file_system_type *get_fs_type(con
 LIST_HEAD(super_blocks);
 DEFINE_SPINLOCK(sb_lock);
 
+EXPORT_SYMBOL(super_blocks);
+EXPORT_SYMBOL(sb_lock);
+
 /**
  *	alloc_super	-	create new superblock
  *	@type:	filesystem type superblock should belong to
--- linux-2.6.23-rc6.orig/mm/vmscan.c
+++ linux-2.6.23-rc6/mm/vmscan.c
@@ -212,6 +212,7 @@ unsigned long shrink_slab(unsigned long 
 	up_read(&shrinker_rwsem);
 	return ret;
 }
+EXPORT_SYMBOL(shrink_slab);
 
 /* Called without lock on whether page is mapped, so answer is unstable */
 static inline int page_mapping_inuse(struct page *page)
--- linux-2.6.23-rc6.orig/Documentation/filesystems/proc.txt
+++ linux-2.6.23-rc6/Documentation/filesystems/proc.txt
@@ -263,6 +263,7 @@ Table 1-4: Kernel info in /proc
  driver	     Various drivers grouped here, currently rtc (2.4)
  execdomains Execdomains, related to security			(2.4)
  fb	     Frame Buffer devices				(2.4)
+ filecache   Query/drop in-memory file cache
  fs	     File system parameters, currently nfs/exports	(2.4)
  ide         Directory containing info about the IDE subsystem 
  interrupts  Interrupt usage                                   
@@ -507,6 +508,88 @@ VmallocTotal: total size of vmalloc memo
  VmallocUsed: amount of vmalloc area which is used
 VmallocChunk: largest contigious block of vmalloc area which is free
 
+..............................................................................
+
+filecache:
+
+Provides access to the in-memory file cache.
+
+To list an index of all cached files:
+
+    echo ls > /proc/filecache
+    cat /proc/filecache
+
+The output looks like:
+
+    # filecache 1.0
+    #      ino       size   cached cached%  state   refcnt  dev             file
+       1026334         91       92    100   --      66      03:02(hda2)     /lib/ld-2.3.6.so
+        233608       1242      972     78   --      66      03:02(hda2)     /lib/tls/libc-2.3.6.so
+         65203        651      476     73   --      1       03:02(hda2)     /bin/bash
+       1026445        261      160     61   --      10      03:02(hda2)     /lib/libncurses.so.5.5
+        235427         10       12    100   --      44      03:02(hda2)     /lib/tls/libdl-2.3.6.so
+
+FIELD	INTRO
+---------------------------------------------------------------------------
+ino	inode number
+size	inode size in KB
+cached	cached size in KB
+cached%	percent of file data cached
+state1	'-' clean; 'd' metadata dirty; 'D' data dirty
+state2	'-' unlocked; 'L' locked, normally indicates file being written out
+refcnt	file reference count, it's an in-kernel one, not exactly open count
+dev	major:minor numbers in hex, followed by a descriptive device name
+file	file path _inside_ the filesystem. There are several special names:
+	'(noname)':	the file name is not available
+	'(03:02)':	the file is a block device file of major:minor
+	'...(deleted)': the named file has been deleted from the disk
+
+To list the cached pages of a perticular file:
+
+    echo /bin/bash > /proc/filecache
+    cat /proc/filecache
+
+    # file /bin/bash
+    # flags R:referenced A:active U:uptodate D:dirty W:writeback M:mmap
+    # idx   len     state   refcnt
+    0       36      RAU__M  3
+    36      1       RAU__M  2
+    37      8       RAU__M  3
+    45      2       RAU___  1
+    47      6       RAU__M  3
+    53      3       RAU__M  2
+    56      2       RAU__M  3
+
+FIELD	INTRO
+----------------------------------------------------------------------------
+idx	page index
+len	number of pages which are cached and share the same state
+state	page state of the flags listed in line two
+refcnt	page reference count
+
+Careful users may notice that the file name to be queried is remembered between
+commands. Internally, the module has a global variable to store the file name
+parameter, so that it can be inherited by newly opened /proc/filecache file.
+However it can lead to interference for multiple queriers. The solution here
+is to obey a rule: only root can interactively change the file name parameter;
+normal users must go for scripts to access the interface. Scripts should do it
+by following the code example below:
+
+    filecache = open("/proc/filecache", "rw");
+    # avoid polluting the global parameter filename
+    filecache.write("set private");
+
+To instruct the kernel to drop clean caches, dentries and inodes from memory,
+causing that memory to become free:
+
+    # drop clean file data cache (i.e. file backed pagecache)
+    echo drop pagecache > /proc/filecache
+
+    # drop clean file metadata cache (i.e. dentries and inodes)
+    echo drop slabcache > /proc/filecache
+
+Note that the drop commands are non-destructive operations and dirty objects
+are not freeable, the user should run `sync' first.
 
 1.3 IDE devices in /proc/ide
 ----------------------------
--- /dev/null
+++ linux-2.6.23-rc6/fs/proc/filecache.c
@@ -0,0 +1,934 @@
+/*
+ * fs/proc/filecache.c
+ *
+ * Copyright (C) 2006, 2007 Fengguang Wu <wfg@mail.ustc.edu.cn>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/radix-tree.h>
+#include <linux/page-flags.h>
+#include <linux/pagevec.h>
+#include <linux/pagemap.h>
+#include <linux/vmalloc.h>
+#include <linux/writeback.h>
+#include <linux/buffer_head.h>
+#include <linux/parser.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/file.h>
+#include <linux/module.h>
+#include <asm/uaccess.h>
+
+/*
+ * Increase minor version when new columns are added;
+ * Increase major version when existing columns are changed.
+ */
+#define FILECACHE_VERSION	"1.0"
+
+/* Internal buffer sizes. The larger the more effcient. */
+#define SBUF_SIZE	(128<<10)
+#define IWIN_PAGE_ORDER	3
+#define IWIN_SIZE	((PAGE_SIZE<<IWIN_PAGE_ORDER) / sizeof(struct inode *))
+
+/*
+ * Session management.
+ *
+ * Each opened /proc/filecache file is assiocated with a session object.
+ * Also there is a global_session that maintains status across open()/close()
+ * (i.e. the lifetime of an opened file), so that a casual user can query the
+ * filecache via _multiple_ simple shell commands like
+ * 'echo cat /bin/bash > /proc/filecache; cat /proc/filecache'.
+ *
+ * session.query_file is the file whose cache info is to be queried.
+ * Its value determines what we get on read():
+ * 	- NULL: ii_*() called to show the inode index
+ * 	- filp: pg_*() called to show the page groups of a filp
+ *
+ * session.query_file is
+ * 	- cloned from global_session.query_file on open();
+ * 	- updated on write("cat filename");
+ * 	  note that the new file will also be saved in global_session.query_file if
+ * 	  session.private_session is false.
+ */
+
+struct session {
+	/* options */
+	int		private_session;
+	unsigned long	ls_options;
+	dev_t		ls_dev;
+
+	/* parameters */
+	struct file	*query_file;
+
+	/* seqfile pos */
+	pgoff_t		start_offset;
+	pgoff_t		next_offset;
+
+	/* inode at last pos */
+	struct {
+		unsigned long pos;
+		unsigned long state;
+		struct inode *inode;
+		struct inode *pinned_inode;
+	} ipos;
+
+	/* inode window */
+	struct {
+		unsigned long cursor;
+		unsigned long origin;
+		unsigned long size;
+		struct inode **inodes;
+	} iwin;
+};
+
+static struct session global_session;
+
+/*
+ * Session address is stored in proc_file->f_ra.start:
+ * we assume that there will be no readahead for proc_file.
+ */
+static struct session *get_session(struct file *proc_file)
+{
+	return (struct session *)proc_file->f_ra.start;
+}
+
+static void set_session(struct file *proc_file, struct session *s)
+{
+	BUG_ON(proc_file->f_ra.start);
+	proc_file->f_ra.start = (unsigned long)s;
+}
+
+static void update_global_file(struct session *s)
+{
+	if (s->private_session)
+		return;
+
+	if (global_session.query_file)
+		fput(global_session.query_file);
+
+	global_session.query_file = s->query_file;
+
+	if (global_session.query_file)
+		get_file(global_session.query_file);
+}
+
+/*
+ * Cases of the name:
+ * 1) NULL                (new session)
+ * 	s->query_file = global_session.query_file = 0;
+ * 2) ""                  (ls/la)
+ * 	s->query_file = global_session.query_file;
+ * 3) a regular file name (cat newfile)
+ * 	s->query_file = global_session.query_file = newfile;
+ */
+static int session_update_file(struct session *s, char *name)
+{
+	static DEFINE_MUTEX(mutex); /* protects global_session.query_file */
+	int err = 0;
+
+	mutex_lock(&mutex);
+
+	/*
+	 * We are to quit, or to list the cached files.
+	 * Reset *.query_file.
+	 */
+	if (!name) {
+		if (s->query_file) {
+			fput(s->query_file);
+			s->query_file = NULL;
+		}
+		update_global_file(s);
+		goto out;
+	}
+
+	/*
+	 * This is a new session.
+	 * Inherit options/parameters from global ones.
+	 */
+	if (name[0] == '\0') {
+		*s = global_session;
+		if (s->query_file)
+			get_file(s->query_file);
+		goto out;
+	}
+
+	/*
+	 * Open the named file.
+	 */
+	if (s->query_file)
+		fput(s->query_file);
+	s->query_file = filp_open(name, O_RDONLY|O_LARGEFILE, 0);
+	if (IS_ERR(s->query_file)) {
+		err = PTR_ERR(s->query_file);
+		s->query_file = NULL;
+	} else
+		update_global_file(s);
+
+out:
+	mutex_unlock(&mutex);
+
+	return err;
+}
+
+static struct session *session_create(void)
+{
+	struct session *s;
+	int err = 0;
+
+	s = kmalloc(sizeof(*s), GFP_KERNEL);
+	if (s)
+		err = session_update_file(s, "");
+	else
+		err = -ENOMEM;
+
+	return err ? ERR_PTR(err) : s;
+}
+
+static void session_release(struct session *s)
+{
+	if (s->ipos.pinned_inode)
+		iput(s->ipos.pinned_inode);
+	if (s->query_file)
+		fput(s->query_file);
+	kfree(s);
+}
+
+
+/*
+ * Listing of cached files.
+ *
+ * Usage:
+ * 		echo > /proc/filecache  # enter listing mode
+ * 		cat /proc/filecache     # get the file listing
+ */
+
+/* code style borrowed from ib_srp.c */
+enum {
+	LS_OPT_ERR	=	0,
+	LS_OPT_NOCLEAN	=	1 << 0,
+	LS_OPT_NODIRTY	=	1 << 1,
+	LS_OPT_NOUNUSED	=	1 << 2,
+	LS_OPT_EMPTY	=	1 << 3,
+	LS_OPT_ALL	=	1 << 4,
+	LS_OPT_DEV	=	1 << 5,
+};
+
+static match_table_t ls_opt_tokens = {
+	{ LS_OPT_NOCLEAN,	"noclean" 	},
+	{ LS_OPT_NODIRTY,	"nodirty" 	},
+	{ LS_OPT_NOUNUSED,	"nounused" 	},
+	{ LS_OPT_EMPTY,		"empty"		},
+	{ LS_OPT_ALL,		"all" 		},
+	{ LS_OPT_DEV,		"dev=%s"	},
+	{ LS_OPT_ERR,		NULL 		}
+};
+
+static int ls_parse_options(const char *buf, struct session *s)
+{
+	substring_t args[MAX_OPT_ARGS];
+	char *options, *sep_opt;
+	char *p;
+	int token;
+	int ret = 0;
+
+	if (!buf)
+		return 0;
+	options = kstrdup(buf, GFP_KERNEL);
+	if (!options)
+		return -ENOMEM;
+
+	s->ls_options = 0;
+	sep_opt = options;
+	while ((p = strsep(&sep_opt, " ")) != NULL) {
+		if (!*p)
+			continue;
+
+		token = match_token(p, ls_opt_tokens, args);
+
+		switch (token) {
+		case LS_OPT_NOCLEAN:
+		case LS_OPT_NODIRTY:
+		case LS_OPT_NOUNUSED:
+		case LS_OPT_EMPTY:
+		case LS_OPT_ALL:
+			s->ls_options |= token;
+			break;
+		case LS_OPT_DEV:
+			p = match_strdup(args);
+			if (!p) {
+				ret = -ENOMEM;
+				goto out;
+			}
+			if (*p == '/') {
+				struct kstat stat;
+				struct nameidata nd;
+				ret = path_lookup(p, LOOKUP_FOLLOW, &nd);
+				if (!ret)
+					ret = vfs_getattr(nd.mnt,
+							  nd.dentry, &stat);
+				if (!ret)
+					s->ls_dev = stat.rdev;
+			} else
+				s->ls_dev = simple_strtoul(p, NULL, 0);
+			/* printk("%lx %s\n", (long)s->ls_dev, p); */
+			kfree(p);
+			break;
+
+		default:
+			printk(KERN_WARNING "unknown parameter or missing value "
+			       "'%s' in ls command\n", p);
+			ret = -EINVAL;
+			goto out;
+		}
+	}
+
+out:
+	kfree(options);
+	return ret;
+}
+
+/*
+ * Add possible filters here.
+ * No permission check: we cannot verify the path's permission anyway.
+ * We simply demand root previledge for accessing /proc/filecache.
+ */
+static int may_show_inode(struct session *s, struct inode *inode)
+{
+	if (!atomic_read(&inode->i_count))
+		return 0;
+	if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE))
+		return 0;
+	if (!inode->i_mapping)
+		return 0;
+
+	if (s->ls_dev && s->ls_dev != inode->i_sb->s_dev)
+		return 0;
+
+	if (s->ls_options & LS_OPT_ALL)
+		return 1;
+
+	if (!(s->ls_options & LS_OPT_EMPTY) && !inode->i_mapping->nrpages)
+		return 0;
+
+	if ((s->ls_options & LS_OPT_NOCLEAN) && !(inode->i_state & I_DIRTY))
+		return 0;
+
+	if ((s->ls_options & LS_OPT_NODIRTY) && (inode->i_state & I_DIRTY))
+		return 0;
+
+	if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
+	      S_ISLNK(inode->i_mode) || S_ISBLK(inode->i_mode)))
+		return 0;
+
+	return 1;
+}
+
+/*
+ * Full: there are more data following.
+ */
+static int iwin_full(struct session *s)
+{
+	return !s->iwin.cursor ||
+		s->iwin.cursor > s->iwin.origin + s->iwin.size;
+}
+
+static int iwin_push(struct session *s, struct inode *inode)
+{
+	if (!may_show_inode(s, inode))
+		return 0;
+
+	s->iwin.cursor++;
+
+	if (s->iwin.size >= IWIN_SIZE)
+		return 1;
+
+	if (s->iwin.cursor > s->iwin.origin)
+		s->iwin.inodes[s->iwin.size++] = inode;
+	return 0;
+}
+
+/*
+ * Travease the inode lists in order - newest first.
+ * And fill @s->iwin.inodes with inodes positioned in [@pos, @pos+IWIN_SIZE).
+ */
+static int iwin_fill(struct session *s, unsigned long pos)
+{
+	struct inode *inode;
+	struct super_block *sb;
+
+	s->iwin.origin = pos;
+	s->iwin.cursor = 0;
+	s->iwin.size = 0;
+
+	/*
+	 * We have a cursor inode, clean and expected to be unchanged.
+	 */
+	if (s->ipos.inode && pos >= s->ipos.pos &&
+			!(s->ipos.state & I_DIRTY) &&
+			s->ipos.state == s->ipos.inode->i_state) {
+		inode = s->ipos.inode;
+		s->iwin.cursor = s->ipos.pos;
+		goto continue_from_saved;
+	}
+
+	if (s->ls_options & LS_OPT_NODIRTY)
+		goto clean_inodes;
+
+	spin_lock(&sb_lock);
+	list_for_each_entry(sb, &super_blocks, s_list) {
+		if (s->ls_dev && s->ls_dev != sb->s_dev)
+			continue;
+
+		list_for_each_entry(inode, &sb->s_dirty, i_list) {
+			if (iwin_push(s, inode))
+				goto out_full_unlock;
+		}
+		list_for_each_entry(inode, &sb->s_io, i_list) {
+			if (iwin_push(s, inode))
+				goto out_full_unlock;
+		}
+	}
+	spin_unlock(&sb_lock);
+
+clean_inodes:
+	list_for_each_entry(inode, &inode_in_use, i_list) {
+		if (iwin_push(s, inode))
+			goto out_full;
+continue_from_saved:
+		;
+	}
+
+	if (s->ls_options & LS_OPT_NOUNUSED)
+		return 0;
+
+	list_for_each_entry(inode, &inode_unused, i_list) {
+		if (iwin_push(s, inode))
+			goto out_full;
+	}
+
+	return 0;
+
+out_full_unlock:
+	spin_unlock(&sb_lock);
+out_full:
+	return 1;
+}
+
+static struct inode *iwin_inode(struct session *s, unsigned long pos)
+{
+	if ((iwin_full(s) && pos >= s->iwin.origin + s->iwin.size)
+			  || pos < s->iwin.origin)
+		iwin_fill(s, pos);
+
+	if (pos >= s->iwin.cursor)
+		return NULL;
+
+	s->ipos.pos = pos;
+	s->ipos.inode = s->iwin.inodes[pos - s->iwin.origin];
+	BUG_ON(!s->ipos.inode);
+	return s->ipos.inode;
+}
+
+static void show_inode(struct seq_file *m, struct inode *inode)
+{
+	char state[] = "--"; /* dirty, locked */
+	struct dentry *dentry;
+	loff_t size = i_size_read(inode);
+	unsigned long nrpages;
+	int percent;
+	int refcnt;
+	int shift;
+
+	if (!size)
+		size++;
+
+	if (inode->i_mapping)
+		nrpages = inode->i_mapping->nrpages;
+	else {
+		nrpages = 0;
+		WARN_ON(1);
+	}
+
+	for (shift = 0; (size >> shift) > ULONG_MAX / 128; shift += 12)
+		;
+	percent = min(100UL, (((100 * nrpages) >> shift) << PAGE_CACHE_SHIFT) /
+						(unsigned long)(size >> shift));
+
+	if (inode->i_state & (I_DIRTY_DATASYNC|I_DIRTY_PAGES))
+		state[0] = 'D';
+	else if (inode->i_state & I_DIRTY_SYNC)
+		state[0] = 'd';
+
+	if (inode->i_state & I_LOCK)
+		state[0] = 'L';
+
+	refcnt = 0;
+	list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
+		refcnt += atomic_read(&dentry->d_count);
+	}
+
+	seq_printf(m, "%10lu %10llu %8lu %7d ",
+			inode->i_ino,
+			DIV_ROUND_UP(size, 1024),
+			nrpages << (PAGE_CACHE_SHIFT - 10),
+			percent);
+
+	seq_printf(m, "%6d %5s ",
+			refcnt,
+			state);
+
+#ifdef CONFIG_PROC_FILECACHE_EXTRAS
+	seq_printf(m, "%8u %5u %-16s",
+			inode->i_access_count,
+			inode->i_cuid,
+			inode->i_comm);
+#endif
+
+	seq_printf(m, "%02x:%02x(%s)\t",
+			MAJOR(inode->i_sb->s_dev),
+			MINOR(inode->i_sb->s_dev),
+			inode->i_sb->s_id);
+
+	if (list_empty(&inode->i_dentry)) {
+		if (!atomic_read(&inode->i_count))
+			seq_puts(m, "(noname)\n");
+		else
+			seq_printf(m, "(%02x:%02x)\n",
+					imajor(inode), iminor(inode));
+	} else {
+		dentry = list_entry(inode->i_dentry.next,
+							struct dentry, d_alias);
+		seq_path(m, NULL, dentry, " \t\n\\");
+		seq_putc(m, '\n');
+	}
+}
+
+static int ii_show(struct seq_file *m, void *v)
+{
+	unsigned long index = *(loff_t *) v;
+	struct session *s = m->private;
+        struct inode *inode;
+
+	if (index == 0) {
+		seq_puts(m, "# filecache " FILECACHE_VERSION "\n");
+		seq_puts(m, "#      ino       size   cached cached% "
+				"refcnt state "
+#ifdef CONFIG_PROC_FILECACHE_EXTRAS
+				"accessed   uid process         "
+#endif
+				"dev\t\tfile\n");
+	}
+
+        inode = iwin_inode(s,index);
+	show_inode(m, inode);
+
+	return 0;
+}
+
+static void *ii_start(struct seq_file *m, loff_t *pos)
+{
+	struct session *s = m->private;
+
+	s->iwin.size = 0;
+	s->iwin.inodes = (struct inode **)
+				__get_free_pages( GFP_KERNEL, IWIN_PAGE_ORDER);
+	if (!s->iwin.inodes)
+		return NULL;
+
+	spin_lock(&inode_lock);
+
+	return iwin_inode(s, *pos) ? pos : NULL;
+}
+
+static void *ii_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	struct session *s = m->private;
+
+	(*pos)++;
+	return iwin_inode(s, *pos) ? pos : NULL;
+}
+
+static void ii_stop(struct seq_file *m, void *v)
+{
+	struct session *s = m->private;
+	struct inode *inode = s->ipos.inode;
+
+	if (!s->iwin.inodes)
+		return;
+
+	if (inode) {
+		__iget(inode);
+		s->ipos.state = inode->i_state;
+	}
+	spin_unlock(&inode_lock);
+
+	free_pages((unsigned long) s->iwin.inodes, IWIN_PAGE_ORDER);
+	if (s->ipos.pinned_inode)
+		iput(s->ipos.pinned_inode);
+	s->ipos.pinned_inode = inode;
+}
+
+/*
+ * Listing of cached page ranges of a file.
+ *
+ * Usage:
+ * 		echo 'file name' > /proc/filecache
+ * 		cat /proc/filecache
+ */
+
+unsigned long page_mask;
+#define PG_MMAP		PG_lru		/* reuse any non-relevant flag */
+#define PG_BUFFER	PG_readahead	/* ditto */
+
+/*
+ * Page state names, prefixed by their abbreviations.
+ */
+struct {
+	unsigned long	mask;
+	const char     *name;
+	int		faked;
+} page_flag [] = {
+	{1 << PG_referenced,	"R:referenced",	0},
+	{1 << PG_active,	"A:active",	0},
+	{1 << PG_MMAP,		"M:mmap",	1},
+
+	{1 << PG_uptodate,	"U:uptodate",	0},
+	{1 << PG_dirty,		"D:dirty",	0},
+	{1 << PG_writeback,	"W:writeback",	0},
+
+	{1 << PG_BUFFER,	"B:buffer",	1},
+
+};
+
+static unsigned long page_flags(struct page* page)
+{
+	unsigned long flags;
+
+	flags = page->flags & page_mask;
+
+	if (page_mapped(page))
+		flags |= (1 << PG_MMAP);
+
+	if (page_has_buffers(page))
+		flags |= (1 << PG_BUFFER);
+
+	return flags;
+}
+
+static int pages_similiar(struct page* page0, struct page* page)
+{
+	if (page_count(page0) != page_count(page))
+		return 0;
+
+	if (page_flags(page0) != page_flags(page))
+		return 0;
+
+	return 1;
+}
+
+static void show_range(struct seq_file *m, struct page* page, unsigned long len)
+{
+	int i;
+	unsigned long flags;
+
+	if (!m || !page)
+		return;
+
+	seq_printf(m, "%lu\t%lu\t", page->index, len);
+
+	flags = page_flags(page);
+	for (i = 0; i < ARRAY_SIZE(page_flag); i++)
+		seq_putc(m, (flags & page_flag[i].mask) ?
+					page_flag[i].name[0] : '_');
+
+	seq_printf(m, "\t%d\n", page_count(page));
+}
+
+#define BATCH_LINES	100
+static pgoff_t show_file_cache(struct seq_file *m,
+				struct address_space *mapping, pgoff_t start)
+{
+	int i;
+	int lines = 0;
+	pgoff_t len = 0;
+	struct pagevec pvec;
+	struct page *page;
+	struct page *page0 = NULL;
+
+	for (;;) {
+		pagevec_init(&pvec, 0);
+		pvec.nr = radix_tree_gang_lookup(&mapping->page_tree,
+				(void **)pvec.pages, start + len, PAGEVEC_SIZE);
+
+		if (pvec.nr == 0) {
+			show_range(m, page0, len);
+			start = ULONG_MAX;
+			goto out;
+		}
+
+		if (!page0)
+			page0 = pvec.pages[0];
+
+		for (i = 0; i < pvec.nr; i++) {
+			page = pvec.pages[i];
+
+			if (page->index == start + len &&
+					pages_similiar(page0, page))
+				len++;
+			else {
+				show_range(m, page0, len);
+				page0 = page;
+				start = page->index;
+				len = 1;
+				if (++lines > BATCH_LINES)
+					goto out;
+			}
+		}
+	}
+
+out:
+	return start;
+}
+
+static int pg_show(struct seq_file *m, void *v)
+{
+	struct session *s = m->private;
+	struct file *file = s->query_file;
+	pgoff_t offset;
+
+	if (!file)
+		return ii_show(m, v);
+
+	offset = *(loff_t *) v;
+
+	if (!offset) { /* print header */
+		int i;
+
+		seq_puts(m, "# file ");
+		seq_path(m, file->f_vfsmnt, file->f_dentry, " \t\n\\");
+
+		seq_puts(m, "\n# flags");
+		for (i = 0; i < ARRAY_SIZE(page_flag); i++)
+			seq_printf(m, " %s", page_flag[i].name);
+
+		seq_puts(m, "\n# idx\tlen\tstate\trefcnt\n");
+	}
+
+	s->start_offset = offset;
+	s->next_offset = show_file_cache(m, file->f_mapping, offset);
+
+	return 0;
+}
+
+static void *file_pos(struct file *file, loff_t *pos)
+{
+	loff_t size = i_size_read(file->f_mapping->host);
+	pgoff_t end = DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
+	pgoff_t offset = *pos;
+
+	return offset < end ? pos : NULL;
+}
+
+static void *pg_start(struct seq_file *m, loff_t *pos)
+{
+	struct session *s = m->private;
+	struct file *file = s->query_file;
+	pgoff_t offset = *pos;
+
+	if (!file)
+		return ii_start(m, pos);
+
+	read_lock_irq(&file->f_mapping->tree_lock);
+
+	if (offset - s->start_offset == 1)
+		*pos = s->next_offset;
+	return file_pos(file, pos);
+}
+
+static void *pg_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	struct session *s = m->private;
+	struct file *file = s->query_file;
+
+	if (!file)
+		return ii_next(m, v, pos);
+
+	*pos = s->next_offset;
+	return file_pos(file, pos);
+}
+
+static void pg_stop(struct seq_file *m, void *v)
+{
+	struct session *s = m->private;
+	struct file *file = s->query_file;
+
+	if (!file)
+		return ii_stop(m, v);
+
+	read_unlock_irq(&file->f_mapping->tree_lock);
+}
+
+struct seq_operations seq_filecache_op = {
+	.start	= pg_start,
+	.next	= pg_next,
+	.stop	= pg_stop,
+	.show	= pg_show,
+};
+
+
+/*
+ * Proc file operations.
+ */
+
+static int filecache_open(struct inode *inode, struct file *proc_file)
+{
+	struct seq_file *m;
+	struct session *s;
+	unsigned size;
+	char *buf = 0;
+	int ret;
+
+	if (!try_module_get(THIS_MODULE))
+		return -ENOENT;
+
+	s = session_create();
+	if (IS_ERR(s)) {
+		ret = PTR_ERR(s);
+		goto out;
+	}
+	set_session(proc_file, s);
+
+	size = SBUF_SIZE;
+	buf = kmalloc(size, GFP_KERNEL);
+	if (!buf) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	ret = seq_open(proc_file, &seq_filecache_op);
+	if (!ret) {
+		m = proc_file->private_data;
+		m->private = s;
+		m->buf = buf;
+		m->size = size;
+	}
+
+out:
+	if (ret) {
+		kfree(s);
+		kfree(buf);
+		module_put(THIS_MODULE);
+	}
+	return ret;
+}
+
+static int filecache_release(struct inode *inode, struct file *proc_file)
+{
+	struct session *s = get_session(proc_file);
+	int ret;
+
+	session_release(s);
+	ret = seq_release(inode, proc_file);
+	module_put(THIS_MODULE);
+	return ret;
+}
+
+ssize_t filecache_write(struct file *proc_file, const char __user * buffer,
+			size_t count, loff_t *ppos)
+{
+	struct session *s;
+	char *name;
+	int err = 0;
+
+	if (count >= PATH_MAX + 5)
+		return -ENAMETOOLONG;
+
+	name = kmalloc(count+1, GFP_KERNEL);
+	if (!name)
+		return -ENOMEM;
+
+	if (copy_from_user(name, buffer, count)) {
+		err = -EFAULT;
+		goto out;
+	}
+
+	/* strip the optional newline */
+	if (count && name[count-1] == '\n')
+		name[count-1] = '\0';
+	else
+		name[count] = '\0';
+
+	s = get_session(proc_file);
+	if (!strcmp(name, "set private")) {
+		s->private_session = 1;
+		goto out;
+	}
+
+	if (!strncmp(name, "cat ", 4)) {
+		err = session_update_file(s, name+4);
+		goto out;
+	}
+
+	if (!strncmp(name, "ls", 2)) {
+		err = session_update_file(s, NULL);
+		if (!err)
+			err = ls_parse_options(name+2, s);
+		if (!err && !s->private_session) {
+			global_session.ls_dev = s->ls_dev;
+			global_session.ls_options = s->ls_options;
+		}
+		goto out;
+	}
+
+	/* err = -EINVAL; */
+	err = session_update_file(s, name);
+
+out:
+	kfree(name);
+
+	return err ? err : count;
+}
+
+static struct file_operations proc_filecache_fops = {
+	.owner		= THIS_MODULE,
+	.open		= filecache_open,
+	.release	= filecache_release,
+	.write		= filecache_write,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+};
+
+
+static __init int filecache_init(void)
+{
+	int i;
+	struct proc_dir_entry *entry;
+
+	entry = create_proc_entry("filecache", 0600, NULL);
+	if (entry)
+		entry->proc_fops = &proc_filecache_fops;
+
+	for (page_mask = i = 0; i < ARRAY_SIZE(page_flag); i++)
+		if (!page_flag[i].faked)
+			page_mask |= page_flag[i].mask;
+
+	return 0;
+}
+
+static void filecache_exit(void)
+{
+	remove_proc_entry("filecache", NULL);
+	if (global_session.query_file)
+		fput(global_session.query_file);
+}
+
+MODULE_AUTHOR("Fengguang Wu <wfg@mail.ustc.edu.cn>");
+MODULE_LICENSE("GPL");
+
+module_init(filecache_init);
+module_exit(filecache_exit);
--- linux-2.6.23-rc6.orig/include/linux/fs.h
+++ linux-2.6.23-rc6/include/linux/fs.h
@@ -595,6 +595,12 @@ struct inode {
 	void			*i_security;
 #endif
 	void			*i_private; /* fs or device private pointer */
+
+#ifdef CONFIG_PROC_FILECACHE_EXTRAS
+	unsigned int		i_access_count;	/* opened how many times? */
+	uid_t			i_cuid;		/* opened first by which user? */
+	char			i_comm[16];	/* opened first by which app? */
+#endif
 };
 
 /*
@@ -683,6 +689,13 @@ static inline unsigned imajor(const stru
 	return MAJOR(inode->i_rdev);
 }
 
+static inline void inode_accessed(struct inode *inode)
+{
+#ifdef CONFIG_PROC_FILECACHE_EXTRAS
+	inode->i_access_count++;
+#endif
+}
+
 extern struct block_device *I_BDEV(struct inode *inode);
 
 struct fown_struct {
--- linux-2.6.23-rc6.orig/fs/open.c
+++ linux-2.6.23-rc6/fs/open.c
@@ -765,6 +765,7 @@ static struct file *__dentry_open(struct
 			goto cleanup_all;
 	}
 
+	inode_accessed(inode);
 	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 
 	file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
--- linux-2.6.23-rc6.orig/fs/Kconfig
+++ linux-2.6.23-rc6/fs/Kconfig
@@ -1028,6 +1028,36 @@ config CONFIGFS_FS
 	  Both sysfs and configfs can and should exist together on the
 	  same system. One is not a replacement for the other.
 
+config PROC_FILECACHE
+	tristate "/proc/filecache support"
+	default m
+	depends on PROC_FS
+	help
+	  This option creates a file /proc/filecache which enables one to
+	  query/drop the cached files in memory.
+
+	  A quick start guide:
+
+	  # echo 'ls' > /proc/filecache
+	  # head /proc/filecache
+
+	  # echo 'cat /bin/bash' > /proc/filecache
+	  # head /proc/filecache
+
+	  # echo 'drop pagecache' > /proc/filecache
+	  # echo 'drop slabcache' > /proc/filecache
+
+	  For more details, please check Documentation/filesystems/proc.txt .
+
+	  It can be a handy tool for sysadms and desktop users.
+
+config PROC_FILECACHE_EXTRAS
+	bool "track extra states"
+	default y
+	depends on PROC_FILECACHE
+	help
+	  Track extra states that costs a little more time/space.
+
 endmenu
 
 menu "Miscellaneous filesystems"
--- linux-2.6.23-rc6.orig/fs/proc/Makefile
+++ linux-2.6.23-rc6/fs/proc/Makefile
@@ -2,7 +2,8 @@
 # Makefile for the Linux proc filesystem routines.
 #
 
-obj-$(CONFIG_PROC_FS) += proc.o
+obj-$(CONFIG_PROC_FS)		+= proc.o
+obj-$(CONFIG_PROC_FILECACHE)	+= filecache.o
 
 proc-y			:= nommu.o task_nommu.o
 proc-$(CONFIG_MMU)	:= mmu.o task_mmu.o