On 8/30/23 00:11, Bernd Schubert wrote:
Take a shared lock in fuse_cache_write_iter. This was already
done for FOPEN_DIRECT_IO in
commit 153524053bbb ("fuse: allow non-extending parallel direct
writes on the same file")
but so far missing for plain O_DIRECT. Server side needs
to set FOPEN_PARALLEL_DIRECT_WRITES in order to signal that
it supports parallel dio writes.
Cc: Hao Xu <howeyxu@xxxxxxxxxxx>
Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
Cc: Dharmendra Singh <dsingh@xxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Signed-off-by: Bernd Schubert <bschubert@xxxxxxx>
---
fs/fuse/file.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 6b8b9512c336..a6b99bc80fe7 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1314,6 +1314,10 @@ static bool fuse_dio_wr_exclusive_lock(struct kiocb *iocb, struct iov_iter *from
struct file *file = iocb->ki_filp;
struct fuse_file *ff = file->private_data;
+ /* this function is about direct IO only */
+ if (!(iocb->ki_flags & IOCB_DIRECT))
+ return false;
This means for buffered write in fuse_cache_write_iter(), we grab shared
lock, looks not right.
+
/* server side has to advise that it supports parallel dio writes */
if (!(ff->open_flags & FOPEN_PARALLEL_DIRECT_WRITES))
return false;
@@ -1337,6 +1341,7 @@ static ssize_t fuse_cache_write_iter(struct kiocb *iocb, struct iov_iter *from)
struct inode *inode = mapping->host;
ssize_t err;
struct fuse_conn *fc = get_fuse_conn(inode);
+ bool excl_lock = fuse_dio_wr_exclusive_lock(iocb, from);
if (fc->writeback_cache && !(iocb->ki_flags & IOCB_DIRECT)) {
/* Update size (EOF optimization) and mode (SUID clearing) */
@@ -1355,7 +1360,10 @@ static ssize_t fuse_cache_write_iter(struct kiocb *iocb, struct iov_iter *from)
}
writethrough:
- inode_lock(inode);
+ if (excl_lock)
+ inode_lock(inode);
+ else
+ inode_lock_shared(inode);
err = generic_write_checks(iocb, from);
if (err <= 0)
@@ -1370,6 +1378,9 @@ static ssize_t fuse_cache_write_iter(struct kiocb *iocb, struct iov_iter *from)
goto out;
if (iocb->ki_flags & IOCB_DIRECT) {
+ /* file extending writes will trigger i_size_write - exclusive
+ * lock is needed
+ */
written = generic_file_direct_write(iocb, from);
if (written < 0 || !iov_iter_count(from))
goto out;
@@ -1379,7 +1390,10 @@ static ssize_t fuse_cache_write_iter(struct kiocb *iocb, struct iov_iter *from)
written = fuse_perform_write(iocb, from);
}
out:
- inode_unlock(inode);
+ if (excl_lock)
+ inode_unlock(inode);
+ else
+ inode_unlock_shared(inode);
if (written > 0)
written = generic_write_sync(iocb, written);
