Re: [PATCH 09/13] RFC: nfs: create and destroy inode's layout cache

Benny Halevy
2010-09-13T11:32:12Z

On 2010-09-10 22:43, Trond Myklebust wrote:
> On Thu, 2010-09-02 at 14:00 -0400, Fred Isaman wrote:
>> From: The pNFS Team <linux-nfs@vger.kernel.org>
>>
>> At the start of the io paths, try to grab the relevant layout
>> information. This will initiate the inode's layout cache, but
>> stubs ensure the cache stays empty.
>>
>> Signed-off-by: TBD - melding/reorganization of several patches
>> ---
>> fs/nfs/file.c | 5 ++
>> fs/nfs/inode.c | 3 +
>> fs/nfs/pnfs.c | 140 ++++++++++++++++++++++++++++++++++++++++++++++++
>> fs/nfs/pnfs.h | 39 +++++++++++++
>> fs/nfs/read.c | 3 +
>> include/linux/nfs_fs.h | 3 +
>> 6 files changed, 193 insertions(+), 0 deletions(-)
>>
>> diff --git a/fs/nfs/file.c b/fs/nfs/file.c
>> index eb51bd6..10ebdfb 100644
>> --- a/fs/nfs/file.c
>> +++ b/fs/nfs/file.c
>> @@ -36,6 +36,7 @@
>> #include "internal.h"
>> #include "iostat.h"
>> #include "fscache.h"
>> +#include "pnfs.h"
>>
>> #define NFSDBG_FACILITY NFSDBG_FILE
>>
>> @@ -386,6 +387,10 @@ static int nfs_write_begin(struct file *file, struct address_space *mapping,
>> file->f_path.dentry->d_name.name,
>> mapping->host->i_ino, len, (long long) pos);
>>
>> + pnfs_update_layout(mapping->host,
>> + nfs_file_open_context(file),
>> + IOMODE_RW);
>> +
>> start:
>> /*
>> * Prevent starvation issues if someone is doing a consistency
>> diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
>> index 7d2d6c7..0dc6dad 100644
>> --- a/fs/nfs/inode.c
>> +++ b/fs/nfs/inode.c
>> @@ -48,6 +48,7 @@
>> #include "internal.h"
>> #include "fscache.h"
>> #include "dns_resolve.h"
>> +#include "pnfs.h"
>>
>> #define NFSDBG_FACILITY NFSDBG_VFS
>>
>> @@ -1409,6 +1410,7 @@ void nfs4_evict_inode(struct inode *inode)
>> {
>> truncate_inode_pages(&inode->i_data, 0);
>> end_writeback(inode);
>> + pnfs_destroy_layout(NFS_I(inode));
>> /* If we are holding a delegation, return it! */
>> nfs_inode_return_delegation_noreclaim(inode);
>> /* First call standard NFS clear_inode() code */
>> @@ -1446,6 +1448,7 @@ static inline void nfs4_init_once(struct nfs_inode *nfsi)
>> nfsi->delegation = NULL;
>> nfsi->delegation_state = 0;
>> init_rwsem(&nfsi->rwsem);
>> + nfsi->layout = NULL;
>> #endif
>> }
>>
>> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
>> index 8d503fc..65f923b 100644
>> --- a/fs/nfs/pnfs.c
>> +++ b/fs/nfs/pnfs.c
>> @@ -151,3 +151,143 @@ pnfs_unregister_layoutdriver(struct pnfs_layoutdriver_type *ld_type)
>> spin_unlock(&pnfs_spinlock);
>> }
>> EXPORT_SYMBOL(pnfs_unregister_layoutdriver);
>> +
>> +static void
>> +get_layout_hdr_locked(struct pnfs_layout_hdr *lo)
>> +{
>> + assert_spin_locked(&lo->inode->i_lock);
>> + lo->refcount++;
>> +}
>> +
>> +static void
>> +put_layout_hdr_locked(struct pnfs_layout_hdr *lo)
>> +{
>> + assert_spin_locked(&lo->inode->i_lock);
>> + BUG_ON(lo->refcount <= 0);
>> +
>> + lo->refcount--;
>> + if (!lo->refcount) {
>> + dprintk("%s: freeing layout cache %p\n", __func__, lo);
>> + NFS_I(lo->inode)->layout = NULL;
>> + kfree(lo);
>> + }
>> +}
>> +
>> +void
>> +pnfs_destroy_layout(struct nfs_inode *nfsi)
>> +{
>> + struct pnfs_layout_hdr *lo;
>> +
>> + spin_lock(&nfsi->vfs_inode.i_lock);
>> + lo = nfsi->layout;
>> + if (lo) {
>> + /* Matched by refcount set to 1 in alloc_init_layout_hdr */
>> + put_layout_hdr_locked(lo);
>> + }
>> + spin_unlock(&nfsi->vfs_inode.i_lock);
>> +}
>> +
>> +/* STUB - pretend LAYOUTGET to server failed */
>> +static struct pnfs_layout_segment *
>> +send_layoutget(struct pnfs_layout_hdr *lo,
>> + struct nfs_open_context *ctx,
>> + u32 iomode)
>> +{
>> + struct inode *ino = lo->inode;
>> +
>> + set_bit(lo_fail_bit(iomode), &lo->state);
>> + spin_lock(&ino->i_lock);
>> + put_layout_hdr_locked(lo);
>> + spin_unlock(&ino->i_lock);
>> + return NULL;
>> +}
>> +
>> +static struct pnfs_layout_hdr *
>> +alloc_init_layout_hdr(struct inode *ino)
>> +{
>> + struct pnfs_layout_hdr *lo;
>> +
>> + lo = kzalloc(sizeof(struct pnfs_layout_hdr), GFP_KERNEL);
>> + if (!lo)
>> + return NULL;
>> + lo->refcount = 1;
>> + lo->inode = ino;
>> + return lo;
>> +}
>> +
>> +static struct pnfs_layout_hdr *
>> +pnfs_find_alloc_layout(struct inode *ino)
>> +{
>> + struct nfs_inode *nfsi = NFS_I(ino);
>> + struct pnfs_layout_hdr *new = NULL;
>> +
>> + dprintk("%s Begin ino=%p layout=%p\n", __func__, ino, nfsi->layout);
>> +
>> + assert_spin_locked(&ino->i_lock);
>> + if (nfsi->layout)
>> + return nfsi->layout;
>> +
>> + spin_unlock(&ino->i_lock);
>> + new = alloc_init_layout_hdr(ino);
>> + spin_lock(&ino->i_lock);
>> +
>> + if (likely(nfsi->layout == NULL)) /* Won the race? */
>> + nfsi->layout = new;
>> + else
>> + kfree(new);
>> + return nfsi->layout;
>> +}
>> +
>> +/* STUB - LAYOUTGET never succeeds, so cache is empty */
>> +static struct pnfs_layout_segment *
>> +pnfs_has_layout(struct pnfs_layout_hdr *lo, u32 iomode)
>> +{
>> + return NULL;
>> +}
>> +
>> +/*
>> + * Layout segment is retreived from the server if not cached.
>> + * The appropriate layout segment is referenced and returned to the caller.
>> + */
>> +struct pnfs_layout_segment *
>> +pnfs_update_layout(struct inode *ino,
>> + struct nfs_open_context *ctx,
>> + enum pnfs_iomode iomode)
>> +{
>> + struct nfs_inode *nfsi = NFS_I(ino);
>> + struct pnfs_layout_hdr *lo;
>> + struct pnfs_layout_segment *lseg = NULL;
>> +
>> + if (!pnfs_enabled_sb(NFS_SERVER(ino)))
>> + return NULL;
>> + spin_lock(&ino->i_lock);
>> + lo = pnfs_find_alloc_layout(ino);
>> + if (lo == NULL) {
>> + dprintk("%s ERROR: can't get pnfs_layout_hdr\n", __func__);
>> + goto out_unlock;
>> + }
>> +
>> + /* Check to see if the layout for the given range already exists */
>> + lseg = pnfs_has_layout(lo, iomode);
>> + if (lseg) {
>> + dprintk("%s: Using cached lseg %p for iomode %d)\n",
>> + __func__, lseg, iomode);
>> + goto out_unlock;
>> + }
>> +
>> + /* if LAYOUTGET already failed once we don't try again */
>> + if (test_bit(lo_fail_bit(iomode), &nfsi->layout->state))
>> + goto out_unlock;
>> +
>> + get_layout_hdr_locked(lo);
>> + spin_unlock(&ino->i_lock);
>> +
>> + lseg = send_layoutget(lo, ctx, iomode);
>> +out:
>> + dprintk("%s end, state 0x%lx lseg %p\n", __func__,
>> + nfsi->layout->state, lseg);
>> + return lseg;
>> +out_unlock:
>> + spin_unlock(&ino->i_lock);
>> + goto out;
>> +}
>> diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
>> index 9049b9a..b63b445 100644
>> --- a/fs/nfs/pnfs.h
>> +++ b/fs/nfs/pnfs.h
>> @@ -14,6 +14,11 @@
>>
>> #define LAYOUT_NFSV4_1_MODULE_PREFIX "nfs-layouttype4"
>>
>> +enum {
>> + NFS_LAYOUT_RO_FAILED = 0, /* get ro layout failed stop trying */
>> + NFS_LAYOUT_RW_FAILED, /* get rw layout failed stop trying */
>> +};
>> +
>> /* Per-layout driver specific registration structure */
>> struct pnfs_layoutdriver_type {
>> struct list_head pnfs_tblid;
>> @@ -22,6 +27,12 @@ struct pnfs_layoutdriver_type {
>> struct layoutdriver_io_operations *ld_io_ops;
>> };
>>
>> +struct pnfs_layout_hdr {
>> + int refcount;
> ^^^^^ Why not make this 'unsigned int', and/or 'unsigned long'?

Should be fine, we just need to be careful about underflow/overflow
before changing its value.

Benny