Re: XFS Syncd

Shrinand Javadekar
2015-06-08T21:56:19Z

[-- Attachment #1: Type: text/plain, Size: 6922 bytes --]

I gave this another shot after understanding it better. I now have a
version that doesn't crash. I'm attaching the diff and the new
xfs_buf.c file.
However, in the new version the io_list list doesn't get populated at
all in __xfs_buf_delwri_submit(). I haven't completely familiarized
myself with what callers do with this list. Callers initialize this
list and send a pointer to __xfs_buf_delwri_submit() and expect a
populated list back.

Nonetheless, I ran my experiments after building and inserting the XFS
module with this change. Strangely enough, I see the performance going
down by ~25% compared to the original XFS module.

On Fri, Jun 5, 2015 at 10:31 AM, Shrinand Javadekar
<shrinand@maginatics.com> wrote:
> The file xfs_buf.c seems to have gone through a few revisions. I tried
> to understand the code and make the changes in the 3.16.0 kernel but
> it didn't quite work out. XFS crashed while unmounting the disks.
>
> On Thu, Jun 4, 2015 at 5:59 PM, Shrinand Javadekar
> <shrinand@maginatics.com> wrote:
>> Dave,
>>
>> I believe this code is slightly different from the one I have (kernel
>> v3.16.0). Can you give me a patch for kernel v3.16.0? I have a working
>> setup to try this out.
>>
>> http://lxr.free-electrons.com/source/fs/xfs/xfs_buf.c?v=3.16
>>
>> Thanks in advance.
>> -Shri
>>
>>
>> On Wed, Jun 3, 2015 at 11:23 PM, Dave Chinner <david@fromorbit.com> wrote:
>>> On Thu, Jun 04, 2015 at 12:03:39PM +1000, Dave Chinner wrote:
>>>> Fixing this requires a tweak to the algorithm in
>>>> __xfs_buf_delwri_submit() so that we don't lock an entire list of
>>>> thousands of IOs before starting submission. In the mean time,
>>>> reducing the number of AGs will reduce the impact of this because
>>>> the delayed write submission code will skip buffers that are already
>>>> locked or pinned in memory, and hence an AG under modification at
>>>> the time submission occurs will be skipped by the delwri code.
>>>
>>> You might like to try the patch below on a test machine to see if
>>> it helps with the problem.
>>>
>>> Cheers,
>>>
>>> Dave.
>>> --
>>> Dave Chinner
>>> david@fromorbit.com
>>>
>>> xfs: reduce lock hold times in buffer writeback
>>>
>>> From: Dave Chinner <dchinner@redhat.com>
>>>
>>> Signed-off-by: Dave Chinner <dchinner@redhat.com>
>>> ---
>>> fs/xfs/xfs_buf.c | 80 ++++++++++++++++++++++++++++++++++++++++++--------------
>>> 1 file changed, 61 insertions(+), 19 deletions(-)
>>>
>>> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
>>> index bbe4e9e..8d2cc36 100644
>>> --- a/fs/xfs/xfs_buf.c
>>> +++ b/fs/xfs/xfs_buf.c
>>> @@ -1768,15 +1768,63 @@ xfs_buf_cmp(
>>> return 0;
>>> }
>>>
>>> +static void
>>> +xfs_buf_delwri_submit_buffers(
>>> + struct list_head *buffer_list,
>>> + struct list_head *io_list,
>>> + bool wait)
>>> +{
>>> + struct xfs_buf *bp, *n;
>>> + struct blk_plug plug;
>>> +
>>> + blk_start_plug(&plug);
>>> + list_for_each_entry_safe(bp, n, buffer_list, b_list) {
>>> + bp->b_flags &= ~(_XBF_DELWRI_Q | XBF_ASYNC |
>>> + XBF_WRITE_FAIL);
>>> + bp->b_flags |= XBF_WRITE | XBF_ASYNC;
>>> +
>>> + /*
>>> + * We do all IO submission async. This means if we need
>>> + * to wait for IO completion we need to take an extra
>>> + * reference so the buffer is still valid on the other
>>> + * side. We need to move the buffer onto the io_list
>>> + * at this point so the caller can still access it.
>>> + */
>>> + if (wait) {
>>> + xfs_buf_hold(bp);
>>> + list_move_tail(&bp->b_list, io_list);
>>> + } else
>>> + list_del_init(&bp->b_list);
>>> +
>>> + xfs_buf_submit(bp);
>>> + }
>>> + blk_finish_plug(&plug);
>>> +}
>>> +
>>> +/*
>>> + * submit buffers for write.
>>> + *
>>> + * When we have a large buffer list, we do not want to hold all the buffers
>>> + * locked while we block on the request queue waiting for IO dispatch. To avoid
>>> + * this problem, we lock and submit buffers in groups of 50, thereby minimising
>>> + * the lock hold times for lists which may contain thousands of objects.
>>> + *
>>> + * To do this, we sort the buffer list before we walk the list to lock and
>>> + * submit buffers, and we plug and unplug around each group of buffers we
>>> + * submit.
>>> + */
>>> static int
>>> __xfs_buf_delwri_submit(
>>> struct list_head *buffer_list,
>>> struct list_head *io_list,
>>> bool wait)
>>> {
>>> - struct blk_plug plug;
>>> struct xfs_buf *bp, *n;
>>> + LIST_HEAD (submit_list);
>>> int pinned = 0;
>>> + int count = 0;
>>> +
>>> + list_sort(NULL, buffer_list, xfs_buf_cmp);
>>>
>>> list_for_each_entry_safe(bp, n, buffer_list, b_list) {
>>> if (!wait) {
>>> @@ -1802,30 +1850,24 @@ __xfs_buf_delwri_submit(
>>> continue;
>>> }
>>>
>>> - list_move_tail(&bp->b_list, io_list);
>>> + list_move_tail(&bp->b_list, &submit_list);
>>> trace_xfs_buf_delwri_split(bp, _RET_IP_);
>>> - }
>>> -
>>> - list_sort(NULL, io_list, xfs_buf_cmp);
>>> -
>>> - blk_start_plug(&plug);
>>> - list_for_each_entry_safe(bp, n, io_list, b_list) {
>>> - bp->b_flags &= ~(_XBF_DELWRI_Q | XBF_ASYNC | XBF_WRITE_FAIL);
>>> - bp->b_flags |= XBF_WRITE | XBF_ASYNC;
>>>
>>> /*
>>> - * we do all Io submission async. This means if we need to wait
>>> - * for IO completion we need to take an extra reference so the
>>> - * buffer is still valid on the other side.
>>> + * We do small batches of IO submission to minimise lock hold
>>> + * time and unnecessary writeback of buffers that are hot and
>>> + * would otherwise be relogged and hence not require immediate
>>> + * writeback.
>>> */
>>> - if (wait)
>>> - xfs_buf_hold(bp);
>>> - else
>>> - list_del_init(&bp->b_list);
>>> + if (count++ < 50)
>>> + continue;
>>>
>>> - xfs_buf_submit(bp);
>>> + xfs_buf_delwri_submit_buffers(&submit_list, io_list, wait);
>>> + count = 0;
>>> }
>>> - blk_finish_plug(&plug);
>>> +
>>> + if (!list_empty(&submit_list))
>>> + xfs_buf_delwri_submit_buffers(&submit_list, io_list, wait);
>>>
>>> return pinned;
>>> }

[-- Attachment #2: xfs_diff --]
[-- Type: application/octet-stream, Size: 1795 bytes --]

1758a1759,1782
>
> static void
> xfs_buf_delwri_submit_buffers(
> struct list_head *buffer_list,
> bool wait)
> {
> struct xfs_buf *bp, *n;
> struct blk_plug plug;
>
> blk_start_plug(&plug);
> list_for_each_entry_safe(bp, n, buffer_list, b_list) {
> bp->b_flags &= ~(_XBF_DELWRI_Q | XBF_ASYNC | XBF_WRITE_FAIL);
> bp->b_flags |= XBF_WRITE;
>
> if (!wait) {
> bp->b_flags |= XBF_ASYNC;
> list_del_init(&bp->b_list);
> }
> xfs_bdstrat_cb(bp);
> }
> blk_finish_plug(&plug);
> }
>
>
1765d1788
< struct blk_plug plug;
1767a1791,1794
> LIST_HEAD (submit_list);
> int count = 0;
>
> list_sort(NULL, buffer_list, xfs_buf_cmp);
1793c1820,1821
< list_move_tail(&bp->b_list, io_list);
---
> //list_move_tail(&bp->b_list, io_list);
> list_move_tail(&bp->b_list, &submit_list);
1795c1823,1825
< }
---
> if (count++ < 50) {
> continue;
> }
1797c1827,1829
< list_sort(NULL, io_list, xfs_buf_cmp);
---
> xfs_buf_delwri_submit_buffers(&submit_list, wait);
> count = 0;
> }
1799,1802c1831
< blk_start_plug(&plug);
< list_for_each_entry_safe(bp, n, io_list, b_list) {
< bp->b_flags &= ~(_XBF_DELWRI_Q | XBF_ASYNC | XBF_WRITE_FAIL);
< bp->b_flags |= XBF_WRITE;
---
> // list_sort(NULL, io_list, xfs_buf_cmp);
1804,1810c1833,1835
< if (!wait) {
< bp->b_flags |= XBF_ASYNC;
< list_del_init(&bp->b_list);
< }
< xfs_bdstrat_cb(bp);
< }
< blk_finish_plug(&plug);
---
> if (!list_empty(&submit_list)) {
> xfs_buf_delwri_submit_buffers(&submit_list, wait);
> }

[-- Attachment #3: xfs_buf.c --]
[-- Type: text/x-csrc, Size: 44298 bytes --]

/*
* Copyright (c) 2000-2006 Silicon Graphics, Inc.
* All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it would be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "xfs.h"
#include <linux/stddef.h>
#include <linux/errno.h>
#include <linux/gfp.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/vmalloc.h>
#include <linux/bio.h>
#include <linux/sysctl.h>
#include <linux/proc_fs.h>
#include <linux/workqueue.h>
#include <linux/percpu.h>
#include <linux/blkdev.h>
#include <linux/hash.h>
#include <linux/kthread.h>
#include <linux/migrate.h>
#include <linux/backing-dev.h>
#include <linux/freezer.h>

#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_trace.h"
#include "xfs_log.h"

static kmem_zone_t *xfs_buf_zone;

static struct workqueue_struct *xfslogd_workqueue;

#ifdef XFS_BUF_LOCK_TRACKING
# define XB_SET_OWNER(bp) ((bp)->b_last_holder = current->pid)
# define XB_CLEAR_OWNER(bp) ((bp)->b_last_holder = -1)
# define XB_GET_OWNER(bp) ((bp)->b_last_holder)
#else
# define XB_SET_OWNER(bp) do { } while (0)
# define XB_CLEAR_OWNER(bp) do { } while (0)
# define XB_GET_OWNER(bp) do { } while (0)
#endif

#define xb_to_gfp(flags) \
((((flags) & XBF_READ_AHEAD) ? __GFP_NORETRY : GFP_NOFS) | __GFP_NOWARN)

static inline int
xfs_buf_is_vmapped(
struct xfs_buf *bp)
{
/*
* Return true if the buffer is vmapped.
*
* b_addr is null if the buffer is not mapped, but the code is clever
* enough to know it doesn't have to map a single page, so the check has
* to be both for b_addr and bp->b_page_count > 1.
*/
return bp->b_addr && bp->b_page_count > 1;
}

static inline int
xfs_buf_vmap_len(
struct xfs_buf *bp)
{
return (bp->b_page_count * PAGE_SIZE) - bp->b_offset;
}

/*
* When we mark a buffer stale, we remove the buffer from the LRU and clear the
* b_lru_ref count so that the buffer is freed immediately when the buffer
* reference count falls to zero. If the buffer is already on the LRU, we need
* to remove the reference that LRU holds on the buffer.
*
* This prevents build-up of stale buffers on the LRU.
*/
void
xfs_buf_stale(
struct xfs_buf *bp)
{
ASSERT(xfs_buf_islocked(bp));

bp->b_flags |= XBF_STALE;

/*
* Clear the delwri status so that a delwri queue walker will not
* flush this buffer to disk now that it is stale. The delwri queue has
* a reference to the buffer, so this is safe to do.
*/
bp->b_flags &= ~_XBF_DELWRI_Q;

spin_lock(&bp->b_lock);
atomic_set(&bp->b_lru_ref, 0);
if (!(bp->b_state & XFS_BSTATE_DISPOSE) &&
(list_lru_del(&bp->b_target->bt_lru, &bp->b_lru)))
atomic_dec(&bp->b_hold);

ASSERT(atomic_read(&bp->b_hold) >= 1);
spin_unlock(&bp->b_lock);
}

static int
xfs_buf_get_maps(
struct xfs_buf *bp,
int map_count)
{
ASSERT(bp->b_maps == NULL);
bp->b_map_count = map_count;

if (map_count == 1) {
bp->b_maps = &bp->__b_map;
return 0;
}

bp->b_maps = kmem_zalloc(map_count * sizeof(struct xfs_buf_map),
KM_NOFS);
if (!bp->b_maps)
return ENOMEM;
return 0;
}

/*
* Frees b_pages if it was allocated.
*/
static void
xfs_buf_free_maps(
struct xfs_buf *bp)
{
if (bp->b_maps != &bp->__b_map) {
kmem_free(bp->b_maps);
bp->b_maps = NULL;
}
}

struct xfs_buf *
_xfs_buf_alloc(
struct xfs_buftarg *target,
struct xfs_buf_map *map,
int nmaps,
xfs_buf_flags_t flags)
{
struct xfs_buf *bp;
int error;
int i;

bp = kmem_zone_zalloc(xfs_buf_zone, KM_NOFS);
if (unlikely(!bp))
return NULL;

/*
* We don't want certain flags to appear in b_flags unless they are
* specifically set by later operations on the buffer.
*/
flags &= ~(XBF_UNMAPPED | XBF_TRYLOCK | XBF_ASYNC | XBF_READ_AHEAD);

atomic_set(&bp->b_hold, 1);
atomic_set(&bp->b_lru_ref, 1);
init_completion(&bp->b_iowait);
INIT_LIST_HEAD(&bp->b_lru);
INIT_LIST_HEAD(&bp->b_list);
RB_CLEAR_NODE(&bp->b_rbnode);
sema_init(&bp->b_sema, 0); /* held, no waiters */
spin_lock_init(&bp->b_lock);
XB_SET_OWNER(bp);
bp->b_target = target;
bp->b_flags = flags;

/*
* Set length and io_length to the same value initially.
* I/O routines should use io_length, which will be the same in
* most cases but may be reset (e.g. XFS recovery).
*/
error = xfs_buf_get_maps(bp, nmaps);
if (error) {
kmem_zone_free(xfs_buf_zone, bp);
return NULL;
}

bp->b_bn = map[0].bm_bn;
bp->b_length = 0;
for (i = 0; i < nmaps; i++) {
bp->b_maps[i].bm_bn = map[i].bm_bn;
bp->b_maps[i].bm_len = map[i].bm_len;
bp->b_length += map[i].bm_len;
}
bp->b_io_length = bp->b_length;

atomic_set(&bp->b_pin_count, 0);
init_waitqueue_head(&bp->b_waiters);

XFS_STATS_INC(xb_create);
trace_xfs_buf_init(bp, _RET_IP_);

return bp;
}

/*
* Allocate a page array capable of holding a specified number
* of pages, and point the page buf at it.
*/
STATIC int
_xfs_buf_get_pages(
xfs_buf_t *bp,
int page_count)
{
/* Make sure that we have a page list */
if (bp->b_pages == NULL) {
bp->b_page_count = page_count;
if (page_count <= XB_PAGES) {
bp->b_pages = bp->b_page_array;
} else {
bp->b_pages = kmem_alloc(sizeof(struct page *) *
page_count, KM_NOFS);
if (bp->b_pages == NULL)
return -ENOMEM;
}
memset(bp->b_pages, 0, sizeof(struct page *) * page_count);
}
return 0;
}

/*
* Frees b_pages if it was allocated.
*/
STATIC void
_xfs_buf_free_pages(
xfs_buf_t *bp)
{
if (bp->b_pages != bp->b_page_array) {
kmem_free(bp->b_pages);
bp->b_pages = NULL;
}
}

/*
* Releases the specified buffer.
*
* The modification state of any associated pages is left unchanged.
* The buffer must not be on any hash - use xfs_buf_rele instead for
* hashed and refcounted buffers
*/
void
xfs_buf_free(
xfs_buf_t *bp)
{
trace_xfs_buf_free(bp, _RET_IP_);

ASSERT(list_empty(&bp->b_lru));

if (bp->b_flags & _XBF_PAGES) {
uint i;

if (xfs_buf_is_vmapped(bp))
vm_unmap_ram(bp->b_addr - bp->b_offset,
bp->b_page_count);

for (i = 0; i < bp->b_page_count; i++) {
struct page *page = bp->b_pages[i];

__free_page(page);
}
} else if (bp->b_flags & _XBF_KMEM)
kmem_free(bp->b_addr);
_xfs_buf_free_pages(bp);
xfs_buf_free_maps(bp);
kmem_zone_free(xfs_buf_zone, bp);
}

/*
* Allocates all the pages for buffer in question and builds it's page list.
*/
STATIC int
xfs_buf_allocate_memory(
xfs_buf_t *bp,
uint flags)
{
size_t size;
size_t nbytes, offset;
gfp_t gfp_mask = xb_to_gfp(flags);
unsigned short page_count, i;
xfs_off_t start, end;
int error;

/*
* for buffers that are contained within a single page, just allocate
* the memory from the heap - there's no need for the complexity of
* page arrays to keep allocation down to order 0.
*/
size = BBTOB(bp->b_length);
if (size < PAGE_SIZE) {
bp->b_addr = kmem_alloc(size, KM_NOFS);
if (!bp->b_addr) {
/* low memory - use alloc_page loop instead */
goto use_alloc_page;
}

if (((unsigned long)(bp->b_addr + size - 1) & PAGE_MASK) !=
((unsigned long)bp->b_addr & PAGE_MASK)) {
/* b_addr spans two pages - use alloc_page instead */
kmem_free(bp->b_addr);
bp->b_addr = NULL;
goto use_alloc_page;
}
bp->b_offset = offset_in_page(bp->b_addr);
bp->b_pages = bp->b_page_array;
bp->b_pages[0] = virt_to_page(bp->b_addr);
bp->b_page_count = 1;
bp->b_flags |= _XBF_KMEM;
return 0;
}

use_alloc_page:
start = BBTOB(bp->b_maps[0].bm_bn) >> PAGE_SHIFT;
end = (BBTOB(bp->b_maps[0].bm_bn + bp->b_length) + PAGE_SIZE - 1)
>> PAGE_SHIFT;
page_count = end - start;
error = _xfs_buf_get_pages(bp, page_count);
if (unlikely(error))
return error;

offset = bp->b_offset;
bp->b_flags |= _XBF_PAGES;

for (i = 0; i < bp->b_page_count; i++) {
struct page *page;
uint retries = 0;
retry:
page = alloc_page(gfp_mask);
if (unlikely(page == NULL)) {
if (flags & XBF_READ_AHEAD) {
bp->b_page_count = i;
error = ENOMEM;
goto out_free_pages;
}

/*
* This could deadlock.
*
* But until all the XFS lowlevel code is revamped to
* handle buffer allocation failures we can't do much.
*/
if (!(++retries % 100))
xfs_err(NULL,
"possible memory allocation deadlock in %s (mode:0x%x)",
__func__, gfp_mask);

XFS_STATS_INC(xb_page_retries);
congestion_wait(BLK_RW_ASYNC, HZ/50);
goto retry;
}

XFS_STATS_INC(xb_page_found);

nbytes = min_t(size_t, size, PAGE_SIZE - offset);
size -= nbytes;
bp->b_pages[i] = page;
offset = 0;
}
return 0;

out_free_pages:
for (i = 0; i < bp->b_page_count; i++)
__free_page(bp->b_pages[i]);
return error;
}

/*
* Map buffer into kernel address-space if necessary.
*/
STATIC int
_xfs_buf_map_pages(
xfs_buf_t *bp,
uint flags)
{
ASSERT(bp->b_flags & _XBF_PAGES);
if (bp->b_page_count == 1) {
/* A single page buffer is always mappable */
bp->b_addr = page_address(bp->b_pages[0]) + bp->b_offset;
} else if (flags & XBF_UNMAPPED) {
bp->b_addr = NULL;
} else {
int retried = 0;
unsigned noio_flag;

/*
* vm_map_ram() will allocate auxillary structures (e.g.
* pagetables) with GFP_KERNEL, yet we are likely to be under
* GFP_NOFS context here. Hence we need to tell memory reclaim
* that we are in such a context via PF_MEMALLOC_NOIO to prevent
* memory reclaim re-entering the filesystem here and
* potentially deadlocking.
*/
noio_flag = memalloc_noio_save();
do {
bp->b_addr = vm_map_ram(bp->b_pages, bp->b_page_count,
-1, PAGE_KERNEL);
if (bp->b_addr)
break;
vm_unmap_aliases();
} while (retried++ <= 1);
memalloc_noio_restore(noio_flag);

if (!bp->b_addr)
return -ENOMEM;
bp->b_addr += bp->b_offset;
}

return 0;
}

/*
* Finding and Reading Buffers
*/

/*
* Look up, and creates if absent, a lockable buffer for
* a given range of an inode. The buffer is returned
* locked. No I/O is implied by this call.
*/
xfs_buf_t *
_xfs_buf_find(
struct xfs_buftarg *btp,
struct xfs_buf_map *map,
int nmaps,
xfs_buf_flags_t flags,
xfs_buf_t *new_bp)
{
size_t numbytes;
struct xfs_perag *pag;
struct rb_node **rbp;
struct rb_node *parent;
xfs_buf_t *bp;
xfs_daddr_t blkno = map[0].bm_bn;
xfs_daddr_t eofs;
int numblks = 0;
int i;

for (i = 0; i < nmaps; i++)
numblks += map[i].bm_len;
numbytes = BBTOB(numblks);

/* Check for IOs smaller than the sector size / not sector aligned */
ASSERT(!(numbytes < btp->bt_meta_sectorsize));
ASSERT(!(BBTOB(blkno) & (xfs_off_t)btp->bt_meta_sectormask));

/*
* Corrupted block numbers can get through to here, unfortunately, so we
* have to check that the buffer falls within the filesystem bounds.
*/
eofs = XFS_FSB_TO_BB(btp->bt_mount, btp->bt_mount->m_sb.sb_dblocks);
if (blkno >= eofs) {
/*
* XXX (dgc): we should really be returning EFSCORRUPTED here,
* but none of the higher level infrastructure supports
* returning a specific error on buffer lookup failures.
*/
xfs_alert(btp->bt_mount,
"%s: Block out of range: block 0x%llx, EOFS 0x%llx ",
__func__, blkno, eofs);
WARN_ON(1);
return NULL;
}

/* get tree root */
pag = xfs_perag_get(btp->bt_mount,
xfs_daddr_to_agno(btp->bt_mount, blkno));

/* walk tree */
spin_lock(&pag->pag_buf_lock);
rbp = &pag->pag_buf_tree.rb_node;
parent = NULL;
bp = NULL;
while (*rbp) {
parent = *rbp;
bp = rb_entry(parent, struct xfs_buf, b_rbnode);

if (blkno < bp->b_bn)
rbp = &(*rbp)->rb_left;
else if (blkno > bp->b_bn)
rbp = &(*rbp)->rb_right;
else {
/*
* found a block number match. If the range doesn't
* match, the only way this is allowed is if the buffer
* in the cache is stale and the transaction that made
* it stale has not yet committed. i.e. we are
* reallocating a busy extent. Skip this buffer and
* continue searching to the right for an exact match.
*/
if (bp->b_length != numblks) {
ASSERT(bp->b_flags & XBF_STALE);
rbp = &(*rbp)->rb_right;
continue;
}
atomic_inc(&bp->b_hold);
goto found;
}
}

/* No match found */
if (new_bp) {
rb_link_node(&new_bp->b_rbnode, parent, rbp);
rb_insert_color(&new_bp->b_rbnode, &pag->pag_buf_tree);
/* the buffer keeps the perag reference until it is freed */
new_bp->b_pag = pag;
spin_unlock(&pag->pag_buf_lock);
} else {
XFS_STATS_INC(xb_miss_locked);
spin_unlock(&pag->pag_buf_lock);
xfs_perag_put(pag);
}
return new_bp;

found:
spin_unlock(&pag->pag_buf_lock);
xfs_perag_put(pag);

if (!xfs_buf_trylock(bp)) {
if (flags & XBF_TRYLOCK) {
xfs_buf_rele(bp);
XFS_STATS_INC(xb_busy_locked);
return NULL;
}
xfs_buf_lock(bp);
XFS_STATS_INC(xb_get_locked_waited);
}

/*
* if the buffer is stale, clear all the external state associated with
* it. We need to keep flags such as how we allocated the buffer memory
* intact here.
*/
if (bp->b_flags & XBF_STALE) {
ASSERT((bp->b_flags & _XBF_DELWRI_Q) == 0);
ASSERT(bp->b_iodone == NULL);
bp->b_flags &= _XBF_KMEM | _XBF_PAGES;
bp->b_ops = NULL;
}

trace_xfs_buf_find(bp, flags, _RET_IP_);
XFS_STATS_INC(xb_get_locked);
return bp;
}

/*
* Assembles a buffer covering the specified range. The code is optimised for
* cache hits, as metadata intensive workloads will see 3 orders of magnitude
* more hits than misses.
*/
struct xfs_buf *
xfs_buf_get_map(
struct xfs_buftarg *target,
struct xfs_buf_map *map,
int nmaps,
xfs_buf_flags_t flags)
{
struct xfs_buf *bp;
struct xfs_buf *new_bp;
int error = 0;

bp = _xfs_buf_find(target, map, nmaps, flags, NULL);
if (likely(bp))
goto found;

new_bp = _xfs_buf_alloc(target, map, nmaps, flags);
if (unlikely(!new_bp))
return NULL;

error = xfs_buf_allocate_memory(new_bp, flags);
if (error) {
xfs_buf_free(new_bp);
return NULL;
}

bp = _xfs_buf_find(target, map, nmaps, flags, new_bp);
if (!bp) {
xfs_buf_free(new_bp);
return NULL;
}

if (bp != new_bp)
xfs_buf_free(new_bp);

found:
if (!bp->b_addr) {
error = _xfs_buf_map_pages(bp, flags);
if (unlikely(error)) {
xfs_warn(target->bt_mount,
"%s: failed to map pagesn", __func__);
xfs_buf_relse(bp);
return NULL;
}
}

XFS_STATS_INC(xb_get);
trace_xfs_buf_get(bp, flags, _RET_IP_);
return bp;
}

STATIC int
_xfs_buf_read(
xfs_buf_t *bp,
xfs_buf_flags_t flags)
{
ASSERT(!(flags & XBF_WRITE));
ASSERT(bp->b_maps[0].bm_bn != XFS_BUF_DADDR_NULL);

bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_READ_AHEAD);
bp->b_flags |= flags & (XBF_READ | XBF_ASYNC | XBF_READ_AHEAD);

xfs_buf_iorequest(bp);
if (flags & XBF_ASYNC)
return 0;
return xfs_buf_iowait(bp);
}

xfs_buf_t *
xfs_buf_read_map(
struct xfs_buftarg *target,
struct xfs_buf_map *map,
int nmaps,
xfs_buf_flags_t flags,
const struct xfs_buf_ops *ops)
{
struct xfs_buf *bp;

flags |= XBF_READ;

bp = xfs_buf_get_map(target, map, nmaps, flags);
if (bp) {
trace_xfs_buf_read(bp, flags, _RET_IP_);

if (!XFS_BUF_ISDONE(bp)) {
XFS_STATS_INC(xb_get_read);
bp->b_ops = ops;
_xfs_buf_read(bp, flags);
} else if (flags & XBF_ASYNC) {
/*
* Read ahead call which is already satisfied,
* drop the buffer
*/
xfs_buf_relse(bp);
return NULL;
} else {
/* We do not want read in the flags */
bp->b_flags &= ~XBF_READ;
}
}

return bp;
}

/*
* If we are not low on memory then do the readahead in a deadlock
* safe manner.
*/
void
xfs_buf_readahead_map(
struct xfs_buftarg *target,
struct xfs_buf_map *map,
int nmaps,
const struct xfs_buf_ops *ops)
{
if (bdi_read_congested(target->bt_bdi))
return;

xfs_buf_read_map(target, map, nmaps,
XBF_TRYLOCK|XBF_ASYNC|XBF_READ_AHEAD, ops);
}

/*
* Read an uncached buffer from disk. Allocates and returns a locked
* buffer containing the disk contents or nothing.
*/
struct xfs_buf *
xfs_buf_read_uncached(
struct xfs_buftarg *target,
xfs_daddr_t daddr,
size_t numblks,
int flags,
const struct xfs_buf_ops *ops)
{
struct xfs_buf *bp;

bp = xfs_buf_get_uncached(target, numblks, flags);
if (!bp)
return NULL;

/* set up the buffer for a read IO */
ASSERT(bp->b_map_count == 1);
bp->b_bn = daddr;
bp->b_maps[0].bm_bn = daddr;
bp->b_flags |= XBF_READ;
bp->b_ops = ops;

if (XFS_FORCED_SHUTDOWN(target->bt_mount)) {
xfs_buf_relse(bp);
return NULL;
}
xfs_buf_iorequest(bp);
xfs_buf_iowait(bp);
return bp;
}

/*
* Return a buffer allocated as an empty buffer and associated to external
* memory via xfs_buf_associate_memory() back to it's empty state.
*/
void
xfs_buf_set_empty(
struct xfs_buf *bp,
size_t numblks)
{
if (bp->b_pages)
_xfs_buf_free_pages(bp);

bp->b_pages = NULL;
bp->b_page_count = 0;
bp->b_addr = NULL;
bp->b_length = numblks;
bp->b_io_length = numblks;

ASSERT(bp->b_map_count == 1);
bp->b_bn = XFS_BUF_DADDR_NULL;
bp->b_maps[0].bm_bn = XFS_BUF_DADDR_NULL;
bp->b_maps[0].bm_len = bp->b_length;
}

static inline struct page *
mem_to_page(
void *addr)
{
if ((!is_vmalloc_addr(addr))) {
return virt_to_page(addr);
} else {
return vmalloc_to_page(addr);
}
}

int
xfs_buf_associate_memory(
xfs_buf_t *bp,
void *mem,
size_t len)
{
int rval;
int i = 0;
unsigned long pageaddr;
unsigned long offset;
size_t buflen;
int page_count;

pageaddr = (unsigned long)mem & PAGE_MASK;
offset = (unsigned long)mem - pageaddr;
buflen = PAGE_ALIGN(len + offset);
page_count = buflen >> PAGE_SHIFT;

/* Free any previous set of page pointers */
if (bp->b_pages)
_xfs_buf_free_pages(bp);

bp->b_pages = NULL;
bp->b_addr = mem;

rval = _xfs_buf_get_pages(bp, page_count);
if (rval)
return rval;

bp->b_offset = offset;

for (i = 0; i < bp->b_page_count; i++) {
bp->b_pages[i] = mem_to_page((void *)pageaddr);
pageaddr += PAGE_SIZE;
}

bp->b_io_length = BTOBB(len);
bp->b_length = BTOBB(buflen);

return 0;
}

xfs_buf_t *
xfs_buf_get_uncached(
struct xfs_buftarg *target,
size_t numblks,
int flags)
{
unsigned long page_count;
int error, i;
struct xfs_buf *bp;
DEFINE_SINGLE_BUF_MAP(map, XFS_BUF_DADDR_NULL, numblks);

bp = _xfs_buf_alloc(target, &map, 1, 0);
if (unlikely(bp == NULL))
goto fail;

page_count = PAGE_ALIGN(numblks << BBSHIFT) >> PAGE_SHIFT;
error = _xfs_buf_get_pages(bp, page_count);
if (error)
goto fail_free_buf;

for (i = 0; i < page_count; i++) {
bp->b_pages[i] = alloc_page(xb_to_gfp(flags));
if (!bp->b_pages[i])
goto fail_free_mem;
}
bp->b_flags |= _XBF_PAGES;

error = _xfs_buf_map_pages(bp, 0);
if (unlikely(error)) {
xfs_warn(target->bt_mount,
"%s: failed to map pages", __func__);
goto fail_free_mem;
}

trace_xfs_buf_get_uncached(bp, _RET_IP_);
return bp;

fail_free_mem:
while (--i >= 0)
__free_page(bp->b_pages[i]);
_xfs_buf_free_pages(bp);
fail_free_buf:
xfs_buf_free_maps(bp);
kmem_zone_free(xfs_buf_zone, bp);
fail:
return NULL;
}

/*
* Increment reference count on buffer, to hold the buffer concurrently
* with another thread which may release (free) the buffer asynchronously.
* Must hold the buffer already to call this function.
*/
void
xfs_buf_hold(
xfs_buf_t *bp)
{
trace_xfs_buf_hold(bp, _RET_IP_);
atomic_inc(&bp->b_hold);
}

/*
* Releases a hold on the specified buffer. If the
* the hold count is 1, calls xfs_buf_free.
*/
void
xfs_buf_rele(
xfs_buf_t *bp)
{
struct xfs_perag *pag = bp->b_pag;

trace_xfs_buf_rele(bp, _RET_IP_);

if (!pag) {
ASSERT(list_empty(&bp->b_lru));
ASSERT(RB_EMPTY_NODE(&bp->b_rbnode));
if (atomic_dec_and_test(&bp->b_hold))
xfs_buf_free(bp);
return;
}

ASSERT(!RB_EMPTY_NODE(&bp->b_rbnode));

ASSERT(atomic_read(&bp->b_hold) > 0);
if (atomic_dec_and_lock(&bp->b_hold, &pag->pag_buf_lock)) {
spin_lock(&bp->b_lock);
if (!(bp->b_flags & XBF_STALE) && atomic_read(&bp->b_lru_ref)) {
/*
* If the buffer is added to the LRU take a new
* reference to the buffer for the LRU and clear the
* (now stale) dispose list state flag
*/
if (list_lru_add(&bp->b_target->bt_lru, &bp->b_lru)) {
bp->b_state &= ~XFS_BSTATE_DISPOSE;
atomic_inc(&bp->b_hold);
}
spin_unlock(&bp->b_lock);
spin_unlock(&pag->pag_buf_lock);
} else {
/*
* most of the time buffers will already be removed from
* the LRU, so optimise that case by checking for the
* XFS_BSTATE_DISPOSE flag indicating the last list the
* buffer was on was the disposal list
*/
if (!(bp->b_state & XFS_BSTATE_DISPOSE)) {
list_lru_del(&bp->b_target->bt_lru, &bp->b_lru);
} else {
ASSERT(list_empty(&bp->b_lru));
}
spin_unlock(&bp->b_lock);

ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
rb_erase(&bp->b_rbnode, &pag->pag_buf_tree);
spin_unlock(&pag->pag_buf_lock);
xfs_perag_put(pag);
xfs_buf_free(bp);
}
}
}

/*
* Lock a buffer object, if it is not already locked.
*
* If we come across a stale, pinned, locked buffer, we know that we are
* being asked to lock a buffer that has been reallocated. Because it is
* pinned, we know that the log has not been pushed to disk and hence it
* will still be locked. Rather than continuing to have trylock attempts
* fail until someone else pushes the log, push it ourselves before
* returning. This means that the xfsaild will not get stuck trying
* to push on stale inode buffers.
*/
int
xfs_buf_trylock(
struct xfs_buf *bp)
{
int locked;

locked = down_trylock(&bp->b_sema) == 0;
if (locked)
XB_SET_OWNER(bp);

trace_xfs_buf_trylock(bp, _RET_IP_);
return locked;
}

/*
* Lock a buffer object.
*
* If we come across a stale, pinned, locked buffer, we know that we
* are being asked to lock a buffer that has been reallocated. Because
* it is pinned, we know that the log has not been pushed to disk and
* hence it will still be locked. Rather than sleeping until someone
* else pushes the log, push it ourselves before trying to get the lock.
*/
void
xfs_buf_lock(
struct xfs_buf *bp)
{
trace_xfs_buf_lock(bp, _RET_IP_);

if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
xfs_log_force(bp->b_target->bt_mount, 0);
down(&bp->b_sema);
XB_SET_OWNER(bp);

trace_xfs_buf_lock_done(bp, _RET_IP_);
}

void
xfs_buf_unlock(
struct xfs_buf *bp)
{
XB_CLEAR_OWNER(bp);
up(&bp->b_sema);

trace_xfs_buf_unlock(bp, _RET_IP_);
}

STATIC void
xfs_buf_wait_unpin(
xfs_buf_t *bp)
{
DECLARE_WAITQUEUE (wait, current);

if (atomic_read(&bp->b_pin_count) == 0)
return;

add_wait_queue(&bp->b_waiters, &wait);
for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
if (atomic_read(&bp->b_pin_count) == 0)
break;
io_schedule();
}
remove_wait_queue(&bp->b_waiters, &wait);
set_current_state(TASK_RUNNING);
}

/*
* Buffer Utility Routines
*/

STATIC void
xfs_buf_iodone_work(
struct work_struct *work)
{
struct xfs_buf *bp =
container_of(work, xfs_buf_t, b_iodone_work);
bool read = !!(bp->b_flags & XBF_READ);

bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD);

/* only validate buffers that were read without errors */
if (read && bp->b_ops && !bp->b_error && (bp->b_flags & XBF_DONE))
bp->b_ops->verify_read(bp);

if (bp->b_iodone)
(*(bp->b_iodone))(bp);
else if (bp->b_flags & XBF_ASYNC)
xfs_buf_relse(bp);
else {
ASSERT(read && bp->b_ops);
complete(&bp->b_iowait);
}
}

void
xfs_buf_ioend(
struct xfs_buf *bp,
int schedule)
{
bool read = !!(bp->b_flags & XBF_READ);

trace_xfs_buf_iodone(bp, _RET_IP_);

if (bp->b_error == 0)
bp->b_flags |= XBF_DONE;

if (bp->b_iodone || (read && bp->b_ops) || (bp->b_flags & XBF_ASYNC)) {
if (schedule) {
INIT_WORK(&bp->b_iodone_work, xfs_buf_iodone_work);
queue_work(xfslogd_workqueue, &bp->b_iodone_work);
} else {
xfs_buf_iodone_work(&bp->b_iodone_work);
}
} else {
bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD);
complete(&bp->b_iowait);
}
}

void
xfs_buf_ioerror(
xfs_buf_t *bp,
int error)
{
ASSERT(error >= 0 && error <= 0xffff);
bp->b_error = (unsigned short)error;
trace_xfs_buf_ioerror(bp, error, _RET_IP_);
}

void
xfs_buf_ioerror_alert(
struct xfs_buf *bp,
const char *func)
{
xfs_alert(bp->b_target->bt_mount,
"metadata I/O error: block 0x%llx (\"%s\") error %d numblks %d",
(__uint64_t)XFS_BUF_ADDR(bp), func, bp->b_error, bp->b_length);
}

/*
* Called when we want to stop a buffer from getting written or read.
* We attach the EIO error, muck with its flags, and call xfs_buf_ioend
* so that the proper iodone callbacks get called.
*/
STATIC int
xfs_bioerror(
xfs_buf_t *bp)
{
#ifdef XFSERRORDEBUG
ASSERT(XFS_BUF_ISREAD(bp) || bp->b_iodone);
#endif

/*
* No need to wait until the buffer is unpinned, we aren't flushing it.
*/
xfs_buf_ioerror(bp, EIO);

/*
* We're calling xfs_buf_ioend, so delete XBF_DONE flag.
*/
XFS_BUF_UNREAD(bp);
XFS_BUF_UNDONE(bp);
xfs_buf_stale(bp);

xfs_buf_ioend(bp, 0);

return EIO;
}

/*
* Same as xfs_bioerror, except that we are releasing the buffer
* here ourselves, and avoiding the xfs_buf_ioend call.
* This is meant for userdata errors; metadata bufs come with
* iodone functions attached, so that we can track down errors.
*/
int
xfs_bioerror_relse(
struct xfs_buf *bp)
{
int64_t fl = bp->b_flags;
/*
* No need to wait until the buffer is unpinned.
* We aren't flushing it.
*
* chunkhold expects B_DONE to be set, whether
* we actually finish the I/O or not. We don't want to
* change that interface.
*/
XFS_BUF_UNREAD(bp);
XFS_BUF_DONE(bp);
xfs_buf_stale(bp);
bp->b_iodone = NULL;
if (!(fl & XBF_ASYNC)) {
/*
* Mark b_error and B_ERROR _both_.
* Lot's of chunkcache code assumes that.
* There's no reason to mark error for
* ASYNC buffers.
*/
xfs_buf_ioerror(bp, EIO);
complete(&bp->b_iowait);
} else {
xfs_buf_relse(bp);
}

return EIO;
}

STATIC int
xfs_bdstrat_cb(
struct xfs_buf *bp)
{
if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
trace_xfs_bdstrat_shut(bp, _RET_IP_);
/*
* Metadata write that didn't get logged but
* written delayed anyway. These aren't associated
* with a transaction, and can be ignored.
*/
if (!bp->b_iodone && !XFS_BUF_ISREAD(bp))
return xfs_bioerror_relse(bp);
else
return xfs_bioerror(bp);
}

xfs_buf_iorequest(bp);
return 0;
}

int
xfs_bwrite(
struct xfs_buf *bp)
{
int error;

ASSERT(xfs_buf_islocked(bp));

bp->b_flags |= XBF_WRITE;
bp->b_flags &= ~(XBF_ASYNC | XBF_READ | _XBF_DELWRI_Q | XBF_WRITE_FAIL);

xfs_bdstrat_cb(bp);

error = xfs_buf_iowait(bp);
if (error) {
xfs_force_shutdown(bp->b_target->bt_mount,
SHUTDOWN_META_IO_ERROR);
}
return error;
}

STATIC void
_xfs_buf_ioend(
xfs_buf_t *bp,
int schedule)
{
if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
xfs_buf_ioend(bp, schedule);
}

STATIC void
xfs_buf_bio_end_io(
struct bio *bio,
int error)
{
xfs_buf_t *bp = (xfs_buf_t *)bio->bi_private;

/*
* don't overwrite existing errors - otherwise we can lose errors on
* buffers that require multiple bios to complete.
*/
if (!bp->b_error)
xfs_buf_ioerror(bp, -error);

if (!bp->b_error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
invalidate_kernel_vmap_range(bp->b_addr, xfs_buf_vmap_len(bp));

_xfs_buf_ioend(bp, 1);
bio_put(bio);
}

static void
xfs_buf_ioapply_map(
struct xfs_buf *bp,
int map,
int *buf_offset,
int *count,
int rw)
{
int page_index;
int total_nr_pages = bp->b_page_count;
int nr_pages;
struct bio *bio;
sector_t sector = bp->b_maps[map].bm_bn;
int size;
int offset;

total_nr_pages = bp->b_page_count;

/* skip the pages in the buffer before the start offset */
page_index = 0;
offset = *buf_offset;
while (offset >= PAGE_SIZE) {
page_index++;
offset -= PAGE_SIZE;
}

/*
* Limit the IO size to the length of the current vector, and update the
* remaining IO count for the next time around.
*/
size = min_t(int, BBTOB(bp->b_maps[map].bm_len), *count);
*count -= size;
*buf_offset += size;

next_chunk:
atomic_inc(&bp->b_io_remaining);
nr_pages = BIO_MAX_SECTORS >> (PAGE_SHIFT - BBSHIFT);
if (nr_pages > total_nr_pages)
nr_pages = total_nr_pages;

bio = bio_alloc(GFP_NOIO, nr_pages);
bio->bi_bdev = bp->b_target->bt_bdev;
bio->bi_iter.bi_sector = sector;
bio->bi_end_io = xfs_buf_bio_end_io;
bio->bi_private = bp;

for (; size && nr_pages; nr_pages--, page_index++) {
int rbytes, nbytes = PAGE_SIZE - offset;

if (nbytes > size)
nbytes = size;

rbytes = bio_add_page(bio, bp->b_pages[page_index], nbytes,
offset);
if (rbytes < nbytes)
break;

offset = 0;
sector += BTOBB(nbytes);
size -= nbytes;
total_nr_pages--;
}

if (likely(bio->bi_iter.bi_size)) {
if (xfs_buf_is_vmapped(bp)) {
flush_kernel_vmap_range(bp->b_addr,
xfs_buf_vmap_len(bp));
}
submit_bio(rw, bio);
if (size)
goto next_chunk;
} else {
/*
* This is guaranteed not to be the last io reference count
* because the caller (xfs_buf_iorequest) holds a count itself.
*/
atomic_dec(&bp->b_io_remaining);
xfs_buf_ioerror(bp, EIO);
bio_put(bio);
}

}

STATIC void
_xfs_buf_ioapply(
struct xfs_buf *bp)
{
struct blk_plug plug;
int rw;
int offset;
int size;
int i;

/*
* Make sure we capture only current IO errors rather than stale errors
* left over from previous use of the buffer (e.g. failed readahead).
*/
bp->b_error = 0;

if (bp->b_flags & XBF_WRITE) {
if (bp->b_flags & XBF_SYNCIO)
rw = WRITE_SYNC;
else
rw = WRITE;
if (bp->b_flags & XBF_FUA)
rw |= REQ_FUA;
if (bp->b_flags & XBF_FLUSH)
rw |= REQ_FLUSH;

/*
* Run the write verifier callback function if it exists. If
* this function fails it will mark the buffer with an error and
* the IO should not be dispatched.
*/
if (bp->b_ops) {
bp->b_ops->verify_write(bp);
if (bp->b_error) {
xfs_force_shutdown(bp->b_target->bt_mount,
SHUTDOWN_CORRUPT_INCORE);
return;
}
}
} else if (bp->b_flags & XBF_READ_AHEAD) {
rw = READA;
} else {
rw = READ;
}

/* we only use the buffer cache for meta-data */
rw |= REQ_META;

/*
* Walk all the vectors issuing IO on them. Set up the initial offset
* into the buffer and the desired IO size before we start -
* _xfs_buf_ioapply_vec() will modify them appropriately for each
* subsequent call.
*/
offset = bp->b_offset;
size = BBTOB(bp->b_io_length);
blk_start_plug(&plug);
for (i = 0; i < bp->b_map_count; i++) {
xfs_buf_ioapply_map(bp, i, &offset, &size, rw);
if (bp->b_error)
break;
if (size <= 0)
break; /* all done */
}
blk_finish_plug(&plug);
}

void
xfs_buf_iorequest(
xfs_buf_t *bp)
{
trace_xfs_buf_iorequest(bp, _RET_IP_);

ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));

if (bp->b_flags & XBF_WRITE)
xfs_buf_wait_unpin(bp);
xfs_buf_hold(bp);

/*
* Set the count to 1 initially, this will stop an I/O
* completion callout which happens before we have started
* all the I/O from calling xfs_buf_ioend too early.
*/
atomic_set(&bp->b_io_remaining, 1);
_xfs_buf_ioapply(bp);
/*
* If _xfs_buf_ioapply failed, we'll get back here with
* only the reference we took above. _xfs_buf_ioend will
* drop it to zero, so we'd better not queue it for later,
* or we'll free it before it's done.
*/
_xfs_buf_ioend(bp, bp->b_error ? 0 : 1);

xfs_buf_rele(bp);
}

/*
* Waits for I/O to complete on the buffer supplied. It returns immediately if
* no I/O is pending or there is already a pending error on the buffer, in which
* case nothing will ever complete. It returns the I/O error code, if any, or
* 0 if there was no error.
*/
int
xfs_buf_iowait(
xfs_buf_t *bp)
{
trace_xfs_buf_iowait(bp, _RET_IP_);

if (!bp->b_error)
wait_for_completion(&bp->b_iowait);

trace_xfs_buf_iowait_done(bp, _RET_IP_);
return bp->b_error;
}

xfs_caddr_t
xfs_buf_offset(
xfs_buf_t *bp,
size_t offset)
{
struct page *page;

if (bp->b_addr)
return bp->b_addr + offset;

offset += bp->b_offset;
page = bp->b_pages[offset >> PAGE_SHIFT];
return (xfs_caddr_t)page_address(page) + (offset & (PAGE_SIZE-1));
}

/*
* Move data into or out of a buffer.
*/
void
xfs_buf_iomove(
xfs_buf_t *bp, /* buffer to process */
size_t boff, /* starting buffer offset */
size_t bsize, /* length to copy */
void *data, /* data address */
xfs_buf_rw_t mode) /* read/write/zero flag */
{
size_t bend;

bend = boff + bsize;
while (boff < bend) {
struct page *page;
int page_index, page_offset, csize;

page_index = (boff + bp->b_offset) >> PAGE_SHIFT;
page_offset = (boff + bp->b_offset) & ~PAGE_MASK;
page = bp->b_pages[page_index];
csize = min_t(size_t, PAGE_SIZE - page_offset,
BBTOB(bp->b_io_length) - boff);

ASSERT((csize + page_offset) <= PAGE_SIZE);

switch (mode) {
case XBRW_ZERO:
memset(page_address(page) + page_offset, 0, csize);
break;
case XBRW_READ:
memcpy(data, page_address(page) + page_offset, csize);
break;
case XBRW_WRITE:
memcpy(page_address(page) + page_offset, data, csize);
}

boff += csize;
data += csize;
}
}

/*
* Handling of buffer targets (buftargs).
*/

/*
* Wait for any bufs with callbacks that have been submitted but have not yet
* returned. These buffers will have an elevated hold count, so wait on those
* while freeing all the buffers only held by the LRU.
*/
static enum lru_status
xfs_buftarg_wait_rele(
struct list_head *item,
spinlock_t *lru_lock,
void *arg)

{
struct xfs_buf *bp = container_of(item, struct xfs_buf, b_lru);
struct list_head *dispose = arg;

if (atomic_read(&bp->b_hold) > 1) {
/* need to wait, so skip it this pass */
trace_xfs_buf_wait_buftarg(bp, _RET_IP_);
return LRU_SKIP;
}
if (!spin_trylock(&bp->b_lock))
return LRU_SKIP;

/*
* clear the LRU reference count so the buffer doesn't get
* ignored in xfs_buf_rele().
*/
atomic_set(&bp->b_lru_ref, 0);
bp->b_state |= XFS_BSTATE_DISPOSE;
list_move(item, dispose);
spin_unlock(&bp->b_lock);
return LRU_REMOVED;
}

void
xfs_wait_buftarg(
struct xfs_buftarg *btp)
{
LIST_HEAD(dispose);
int loop = 0;

/* loop until there is nothing left on the lru list. */
while (list_lru_count(&btp->bt_lru)) {
list_lru_walk(&btp->bt_lru, xfs_buftarg_wait_rele,
&dispose, LONG_MAX);

while (!list_empty(&dispose)) {
struct xfs_buf *bp;
bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
list_del_init(&bp->b_lru);
if (bp->b_flags & XBF_WRITE_FAIL) {
xfs_alert(btp->bt_mount,
"Corruption Alert: Buffer at block 0x%llx had permanent write failures!\n"
"Please run xfs_repair to determine the extent of the problem.",
(long long)bp->b_bn);
}
xfs_buf_rele(bp);
}
if (loop++ != 0)
delay(100);
}
}

static enum lru_status
xfs_buftarg_isolate(
struct list_head *item,
spinlock_t *lru_lock,
void *arg)
{
struct xfs_buf *bp = container_of(item, struct xfs_buf, b_lru);
struct list_head *dispose = arg;

/*
* we are inverting the lru lock/bp->b_lock here, so use a trylock.
* If we fail to get the lock, just skip it.
*/
if (!spin_trylock(&bp->b_lock))
return LRU_SKIP;
/*
* Decrement the b_lru_ref count unless the value is already
* zero. If the value is already zero, we need to reclaim the
* buffer, otherwise it gets another trip through the LRU.
*/
if (!atomic_add_unless(&bp->b_lru_ref, -1, 0)) {
spin_unlock(&bp->b_lock);
return LRU_ROTATE;
}

bp->b_state |= XFS_BSTATE_DISPOSE;
list_move(item, dispose);
spin_unlock(&bp->b_lock);
return LRU_REMOVED;
}

static unsigned long
xfs_buftarg_shrink_scan(
struct shrinker *shrink,
struct shrink_control *sc)
{
struct xfs_buftarg *btp = container_of(shrink,
struct xfs_buftarg, bt_shrinker);
LIST_HEAD(dispose);
unsigned long freed;
unsigned long nr_to_scan = sc->nr_to_scan;

freed = list_lru_walk_node(&btp->bt_lru, sc->nid, xfs_buftarg_isolate,
&dispose, &nr_to_scan);

while (!list_empty(&dispose)) {
struct xfs_buf *bp;
bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
list_del_init(&bp->b_lru);
xfs_buf_rele(bp);
}

return freed;
}

static unsigned long
xfs_buftarg_shrink_count(
struct shrinker *shrink,
struct shrink_control *sc)
{
struct xfs_buftarg *btp = container_of(shrink,
struct xfs_buftarg, bt_shrinker);
return list_lru_count_node(&btp->bt_lru, sc->nid);
}

void
xfs_free_buftarg(
struct xfs_mount *mp,
struct xfs_buftarg *btp)
{
unregister_shrinker(&btp->bt_shrinker);
list_lru_destroy(&btp->bt_lru);

if (mp->m_flags & XFS_MOUNT_BARRIER)
xfs_blkdev_issue_flush(btp);

kmem_free(btp);
}

int
xfs_setsize_buftarg(
xfs_buftarg_t *btp,
unsigned int sectorsize)
{
/* Set up metadata sector size info */
btp->bt_meta_sectorsize = sectorsize;
btp->bt_meta_sectormask = sectorsize - 1;

if (set_blocksize(btp->bt_bdev, sectorsize)) {
char name[BDEVNAME_SIZE];

bdevname(btp->bt_bdev, name);

xfs_warn(btp->bt_mount,
"Cannot set_blocksize to %u on device %s",
sectorsize, name);
return EINVAL;
}

/* Set up device logical sector size mask */
btp->bt_logical_sectorsize = bdev_logical_block_size(btp->bt_bdev);
btp->bt_logical_sectormask = bdev_logical_block_size(btp->bt_bdev) - 1;

return 0;
}

/*
* When allocating the initial buffer target we have not yet
* read in the superblock, so don't know what sized sectors
* are being used at this early stage. Play safe.
*/
STATIC int
xfs_setsize_buftarg_early(
xfs_buftarg_t *btp,
struct block_device *bdev)
{
return xfs_setsize_buftarg(btp, bdev_logical_block_size(bdev));
}

xfs_buftarg_t *
xfs_alloc_buftarg(
struct xfs_mount *mp,
struct block_device *bdev)
{
xfs_buftarg_t *btp;

btp = kmem_zalloc(sizeof(*btp), KM_SLEEP | KM_NOFS);

btp->bt_mount = mp;
btp->bt_dev = bdev->bd_dev;
btp->bt_bdev = bdev;
btp->bt_bdi = blk_get_backing_dev_info(bdev);
if (!btp->bt_bdi)
goto error;

if (xfs_setsize_buftarg_early(btp, bdev))
goto error;

if (list_lru_init(&btp->bt_lru))
goto error;

btp->bt_shrinker.count_objects = xfs_buftarg_shrink_count;
btp->bt_shrinker.scan_objects = xfs_buftarg_shrink_scan;
btp->bt_shrinker.seeks = DEFAULT_SEEKS;
btp->bt_shrinker.flags = SHRINKER_NUMA_AWARE;
register_shrinker(&btp->bt_shrinker);
return btp;

error:
kmem_free(btp);
return NULL;
}

/*
* Add a buffer to the delayed write list.
*
* This queues a buffer for writeout if it hasn't already been. Note that
* neither this routine nor the buffer list submission functions perform
* any internal synchronization. It is expected that the lists are thread-local
* to the callers.
*
* Returns true if we queued up the buffer, or false if it already had
* been on the buffer list.
*/
bool
xfs_buf_delwri_queue(
struct xfs_buf *bp,
struct list_head *list)
{
ASSERT(xfs_buf_islocked(bp));
ASSERT(!(bp->b_flags & XBF_READ));

/*
* If the buffer is already marked delwri it already is queued up
* by someone else for imediate writeout. Just ignore it in that
* case.
*/
if (bp->b_flags & _XBF_DELWRI_Q) {
trace_xfs_buf_delwri_queued(bp, _RET_IP_);
return false;
}

trace_xfs_buf_delwri_queue(bp, _RET_IP_);

/*
* If a buffer gets written out synchronously or marked stale while it
* is on a delwri list we lazily remove it. To do this, the other party
* clears the _XBF_DELWRI_Q flag but otherwise leaves the buffer alone.
* It remains referenced and on the list. In a rare corner case it
* might get readded to a delwri list after the synchronous writeout, in
* which case we need just need to re-add the flag here.
*/
bp->b_flags |= _XBF_DELWRI_Q;
if (list_empty(&bp->b_list)) {
atomic_inc(&bp->b_hold);
list_add_tail(&bp->b_list, list);
}

return true;
}

/*
* Compare function is more complex than it needs to be because
* the return value is only 32 bits and we are doing comparisons
* on 64 bit values
*/
static int
xfs_buf_cmp(
void *priv,
struct list_head *a,
struct list_head *b)
{
struct xfs_buf *ap = container_of(a, struct xfs_buf, b_list);
struct xfs_buf *bp = container_of(b, struct xfs_buf, b_list);
xfs_daddr_t diff;

diff = ap->b_maps[0].bm_bn - bp->b_maps[0].bm_bn;
if (diff < 0)
return -1;
if (diff > 0)
return 1;
return 0;
}

static void
xfs_buf_delwri_submit_buffers(
struct list_head *buffer_list,
bool wait)
{
struct xfs_buf *bp, *n;
struct blk_plug plug;

blk_start_plug(&plug);
list_for_each_entry_safe(bp, n, buffer_list, b_list) {
bp->b_flags &= ~(_XBF_DELWRI_Q | XBF_ASYNC | XBF_WRITE_FAIL);
bp->b_flags |= XBF_WRITE;

if (!wait) {
bp->b_flags |= XBF_ASYNC;
list_del_init(&bp->b_list);
}
xfs_bdstrat_cb(bp);
}
blk_finish_plug(&plug);
}

static int
__xfs_buf_delwri_submit(
struct list_head *buffer_list,
struct list_head *io_list,
bool wait)
{
struct xfs_buf *bp, *n;
int pinned = 0;
LIST_HEAD (submit_list);
int count = 0;

list_sort(NULL, buffer_list, xfs_buf_cmp);

list_for_each_entry_safe(bp, n, buffer_list, b_list) {
if (!wait) {
if (xfs_buf_ispinned(bp)) {
pinned++;
continue;
}
if (!xfs_buf_trylock(bp))
continue;
} else {
xfs_buf_lock(bp);
}

/*
* Someone else might have written the buffer synchronously or
* marked it stale in the meantime. In that case only the
* _XBF_DELWRI_Q flag got cleared, and we have to drop the
* reference and remove it from the list here.
*/
if (!(bp->b_flags & _XBF_DELWRI_Q)) {
list_del_init(&bp->b_list);
xfs_buf_relse(bp);
continue;
}

//list_move_tail(&bp->b_list, io_list);
list_move_tail(&bp->b_list, &submit_list);
trace_xfs_buf_delwri_split(bp, _RET_IP_);
if (count++ < 50) {
continue;
}

xfs_buf_delwri_submit_buffers(&submit_list, wait);
count = 0;
}

// list_sort(NULL, io_list, xfs_buf_cmp);

if (!list_empty(&submit_list)) {
xfs_buf_delwri_submit_buffers(&submit_list, wait);
}

return pinned;
}

/*
* Write out a buffer list asynchronously.
*
* This will take the @buffer_list, write all non-locked and non-pinned buffers
* out and not wait for I/O completion on any of the buffers. This interface
* is only safely useable for callers that can track I/O completion by higher
* level means, e.g. AIL pushing as the @buffer_list is consumed in this
* function.
*/
int
xfs_buf_delwri_submit_nowait(
struct list_head *buffer_list)
{
LIST_HEAD (io_list);
return __xfs_buf_delwri_submit(buffer_list, &io_list, false);
}

/*
* Write out a buffer list synchronously.
*
* This will take the @buffer_list, write all buffers out and wait for I/O
* completion on all of the buffers. @buffer_list is consumed by the function,
* so callers must have some other way of tracking buffers if they require such
* functionality.
*/
int
xfs_buf_delwri_submit(
struct list_head *buffer_list)
{
LIST_HEAD (io_list);
int error = 0, error2;
struct xfs_buf *bp;

__xfs_buf_delwri_submit(buffer_list, &io_list, true);

/* Wait for IO to complete. */
while (!list_empty(&io_list)) {
bp = list_first_entry(&io_list, struct xfs_buf, b_list);

list_del_init(&bp->b_list);
error2 = xfs_buf_iowait(bp);
xfs_buf_relse(bp);
if (!error)
error = error2;
}

return error;
}

int __init
xfs_buf_init(void)
{
xfs_buf_zone = kmem_zone_init_flags(sizeof(xfs_buf_t), "xfs_buf",
KM_ZONE_HWALIGN, NULL);
if (!xfs_buf_zone)
goto out;

xfslogd_workqueue = alloc_workqueue("xfslogd",
WQ_MEM_RECLAIM | WQ_HIGHPRI, 1);
if (!xfslogd_workqueue)
goto out_free_buf_zone;

return 0;

out_free_buf_zone:
kmem_zone_destroy(xfs_buf_zone);
out:
return -ENOMEM;
}

void
xfs_buf_terminate(void)
{
destroy_workqueue(xfslogd_workqueue);
kmem_zone_destroy(xfs_buf_zone);
}

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