This eventually enabled a shared lock for O_DIRECT writes
in fuse_cache_write_iter.
Missing was to check if privileges need to be dropped - if so,
this needs to be done with a exclusive lock.
file_needs_remove_privs and file_remove_privs are both sending
an getxattr call, assumption is that this is rare - should
not have a performance impact.
fuse_dio_wr_exclusive_lock() is not using file_needs_remove_privs,
as it needs to be called again while lock is hold - it would
result in a typical double call into file_needs_remove_privs,
with the expensive xattr retrieval.
Cc: Hao Xu <howeyxu@xxxxxxxxxxx>
Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
Cc: Dharmendra Singh <dsingh@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Signed-off-by: Bernd Schubert <bschubert@xxxxxxx>
---
fs/fuse/file.c | 25 +++++++++++++++++++------
1 file changed, 19 insertions(+), 6 deletions(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 76922a6a0962..feafab9b467f 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1308,7 +1308,8 @@ static bool fuse_io_past_eof(struct kiocb *iocb, struct iov_iter *iter)
/*
* @return true if an exclusive lock for direct IO writes is needed
*/
-static bool fuse_dio_wr_exclusive_lock(struct kiocb *iocb, struct iov_iter *from)
+static bool fuse_dio_wr_exclusive_lock(struct kiocb *iocb, struct iov_iter *from,
+ struct inode *inode)
{
struct file *file = iocb->ki_filp;
struct fuse_file *ff = file->private_data;
@@ -1342,7 +1343,8 @@ 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) || 1;
+ bool excl_lock = fuse_dio_wr_exclusive_lock(iocb, from, inode);
+ int remove_privs = 1;
if (fc->writeback_cache && !(iocb->ki_flags & IOCB_DIRECT)) {
/* Update size (EOF optimization) and mode (SUID clearing) */
@@ -1380,9 +1382,20 @@ static ssize_t fuse_cache_write_iter(struct kiocb *iocb, struct iov_iter *from)
if (err <= 0)
goto out;
- err = file_remove_privs(file);
- if (err)
- goto out;
+ if (!excl_lock) {
+ remove_privs = file_needs_remove_privs(file);
+ if (remove_privs) {
+ inode_unlock_shared(inode);
+ excl_lock = true;
+ goto relock;
+ }
+ }
+
+ if (remove_privs) {
+ err = file_remove_privs(file);
+ if (err)
+ goto out;
+ }
err = file_update_time(file);
if (err)
@@ -1623,7 +1636,7 @@ static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
struct inode *inode = file_inode(iocb->ki_filp);
struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(iocb);
ssize_t res;
- bool exclusive_lock = fuse_dio_wr_exclusive_lock(iocb, from);
+ bool exclusive_lock = fuse_dio_wr_exclusive_lock(iocb, from, inode);
/*
* Take exclusive lock if
--
2.39.2
