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Subject[PATCH] fuse: remove WARN_ON writeback on dead inode
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FUSE has an architectural peculiarity: it cannot write to an inode, unless it
has an associated file open for write. Since the beginning (Apr 30 2008, commit
3be5a52b), FUSE BUG_ON (later WARN_ON) the case when it has to process
writeback, but all associated files are closed. The latest relevant commit is
72523425:

> Don't bug if there's no writable files found for page writeback. If ever
> this is triggered, a WARN_ON helps debugging it much better then a BUG_ON.
>
> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

But that situation can happen in quite a legal way: for example, let's mmap a
file, then issue O_DIRECT read to mmapped region and immediately close file
and munmap. O_DIRECT will pin some pages, execute IO to them and then mark
pages dirty. Here we are.

Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
---
fs/fuse/file.c | 14 +++-----------
1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 6e16dad..3a47aa2 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1624,8 +1624,8 @@ static void fuse_writepage_end(struct fuse_conn *fc, struct fuse_req *req)
fuse_writepage_free(fc, req);
}

-static struct fuse_file *__fuse_write_file_get(struct fuse_conn *fc,
- struct fuse_inode *fi)
+static struct fuse_file *fuse_write_file_get(struct fuse_conn *fc,
+ struct fuse_inode *fi)
{
struct fuse_file *ff = NULL;

@@ -1640,14 +1640,6 @@ static struct fuse_file *__fuse_write_file_get(struct fuse_conn *fc,
return ff;
}

-static struct fuse_file *fuse_write_file_get(struct fuse_conn *fc,
- struct fuse_inode *fi)
-{
- struct fuse_file *ff = __fuse_write_file_get(fc, fi);
- WARN_ON(!ff);
- return ff;
-}
-
int fuse_write_inode(struct inode *inode, struct writeback_control *wbc)
{
struct fuse_conn *fc = get_fuse_conn(inode);
@@ -1655,7 +1647,7 @@ int fuse_write_inode(struct inode *inode, struct writeback_control *wbc)
struct fuse_file *ff;
int err;

- ff = __fuse_write_file_get(fc, fi);
+ ff = fuse_write_file_get(fc, fi);
err = fuse_flush_times(inode, ff);
if (ff)
fuse_file_put(ff, 0);


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