fuse: add blksize field to fuse_attr

There are cases when the filesystem will be passed the buffer from a single
read or write call, namely:

 1) in 'direct-io' mode (not O_DIRECT), read/write requests don't go
    through the page cache, but go directly to the userspace fs

 2) currently buffered writes are done with single page requests, but
    if Nick's ->perform_write() patch goes it, it will be possible to
    do larger write requests.  But only if the original write() was
    also bigger than a page.

In these cases the filesystem might want to give a hint to the app
about the optimal I/O size.

Allow the userspace filesystem to supply a blksize value to be returned by
stat() and friends.  If the field is zero, it defaults to the old
PAGE_CACHE_SIZE value.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 49d716036ea7..9a68d6970845 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -148,6 +148,11 @@ void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
         inode->i_ctime.tv_sec   = attr->ctime;
         inode->i_ctime.tv_nsec  = attr->ctimensec;
 
+        if (attr->blksize != 0)
+                inode->i_blkbits = ilog2(attr->blksize);
+        else
+                inode->i_blkbits = inode->i_sb->s_blocksize_bits;
+
         /*
          * Don't set the sticky bit in i_mode, unless we want the VFS
          * to check permissions.  This prevents failures due to the