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authorMaxim Patlasov <MPatlasov@parallels.com>2013-06-13 12:16:39 +0400
committerMiklos Szeredi <mszeredi@suse.cz>2013-06-18 01:39:03 +0200
commit14c14414d157ea851119c96c61a17306a2b4a035 (patch)
treede18c44d2398a16d3248847b424d5cabd619b7bf /fs/fuse
parent8177a9d79c0e942dcac3312f15585d0344d505a5 (diff)
fuse: hold i_mutex in fuse_file_fallocate()
Changing size of a file on server and local update (fuse_write_update_size) should be always protected by inode->i_mutex. Otherwise a race like this is possible: 1. Process 'A' calls fallocate(2) to extend file (~FALLOC_FL_KEEP_SIZE). fuse_file_fallocate() sends FUSE_FALLOCATE request to the server. 2. Process 'B' calls ftruncate(2) shrinking the file. fuse_do_setattr() sends shrinking FUSE_SETATTR request to the server and updates local i_size by i_size_write(inode, outarg.attr.size). 3. Process 'A' resumes execution of fuse_file_fallocate() and calls fuse_write_update_size(inode, offset + length). But 'offset + length' was obsoleted by ftruncate from previous step. Changed in v2 (thanks Brian and Anand for suggestions): - made relation between mutex_lock() and fuse_set_nowrite(inode) more explicit and clear. - updated patch description to use ftruncate(2) in example Signed-off-by: Maxim V. Patlasov <MPatlasov@parallels.com> Reviewed-by: Brian Foster <bfoster@redhat.com> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Diffstat (limited to 'fs/fuse')
-rw-r--r--fs/fuse/file.c12
1 files changed, 8 insertions, 4 deletions
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index e570081f9f7..35f28103314 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2470,13 +2470,16 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
.mode = mode
};
int err;
+ bool lock_inode = !(mode & FALLOC_FL_KEEP_SIZE) ||
+ (mode & FALLOC_FL_PUNCH_HOLE);
if (fc->no_fallocate)
return -EOPNOTSUPP;
- if (mode & FALLOC_FL_PUNCH_HOLE) {
+ if (lock_inode) {
mutex_lock(&inode->i_mutex);
- fuse_set_nowrite(inode);
+ if (mode & FALLOC_FL_PUNCH_HOLE)
+ fuse_set_nowrite(inode);
}
req = fuse_get_req_nopages(fc);
@@ -2511,8 +2514,9 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
fuse_invalidate_attr(inode);
out:
- if (mode & FALLOC_FL_PUNCH_HOLE) {
- fuse_release_nowrite(inode);
+ if (lock_inode) {
+ if (mode & FALLOC_FL_PUNCH_HOLE)
+ fuse_release_nowrite(inode);
mutex_unlock(&inode->i_mutex);
}