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authorChristoph Hellwig <hch@lst.de>2014-09-10 19:23:30 +0400
committerTrond Myklebust <trond.myklebust@primarydata.com>2014-09-10 23:47:02 +0400
commit612aa983a041056c3368aacfdc9febd406d245a8 (patch)
tree61607917bd96095c5f35784593298fd7581b8b6c /fs/nfs/pnfs.h
parent7c5d187581f57657de79e795602d9f1a0254c88c (diff)
downloadlinux-612aa983a041056c3368aacfdc9febd406d245a8.tar.xz
pnfs: add flag to force read-modify-write in ->write_begin
Like all block based filesystems, the pNFS block layout driver can't read or write at a byte granularity and thus has to perform read-modify-write cycles on writes smaller than this granularity. Add a flag so that the core NFS code always reads a whole page when starting a smaller write, so that we can do it in the place where the VFS expects it instead of doing in very deadlock prone way in the writeback handler. Note that in theory we could do less than page size reads here for disks that have a smaller sector size which are served by a server with a smaller pnfs block size. But so far that doesn't seem like a worthwhile optimization. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Diffstat (limited to 'fs/nfs/pnfs.h')
-rw-r--r--fs/nfs/pnfs.h15
1 files changed, 15 insertions, 0 deletions
diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index 8835b5a320cc..a4c530e52149 100644
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -72,6 +72,7 @@ enum layoutdriver_policy_flags {
/* Should the pNFS client commit and return the layout upon a setattr */
PNFS_LAYOUTRET_ON_SETATTR = 1 << 0,
PNFS_LAYOUTRET_ON_ERROR = 1 << 1,
+ PNFS_READ_WHOLE_PAGE = 1 << 2,
};
struct nfs4_deviceid_node;
@@ -370,6 +371,14 @@ pnfs_ld_layoutret_on_setattr(struct inode *inode)
}
static inline bool
+pnfs_ld_read_whole_page(struct inode *inode)
+{
+ if (!pnfs_enabled_sb(NFS_SERVER(inode)))
+ return false;
+ return NFS_SERVER(inode)->pnfs_curr_ld->flags & PNFS_READ_WHOLE_PAGE;
+}
+
+static inline bool
pnfs_layoutcommit_outstanding(struct inode *inode)
{
struct nfs_inode *nfsi = NFS_I(inode);
@@ -445,6 +454,12 @@ pnfs_ld_layoutret_on_setattr(struct inode *inode)
}
static inline bool
+pnfs_ld_read_whole_page(struct inode *inode)
+{
+ return false;
+}
+
+static inline bool
pnfs_roc(struct inode *ino)
{
return false;