On 9/21/20 10:43 AM, Goldwyn Rodrigues wrote:
From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
Direct writes within EOF are safe to be performed with inode shared lock
to improve parallelization with other direct writes or reads because EOF
is not changed and there is no race with truncate().
Direct reads are already performed under shared inode lock.
This patch is precursor to removing btrfs_inode->dio_sem.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
---
fs/btrfs/file.c | 33 +++++++++++++++++++++------------
1 file changed, 21 insertions(+), 12 deletions(-)
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index d9c3be19d7b3..50092d24eee2 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1977,7 +1977,6 @@ static ssize_t btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
loff_t pos;
ssize_t written = 0;
- bool relock = false;
ssize_t written_buffered;
loff_t endbyte;
int err;
@@ -1986,6 +1985,15 @@ static ssize_t btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
if (iocb->ki_flags & IOCB_NOWAIT)
ilock_flags |= BTRFS_ILOCK_TRY;
+ /*
+ * If the write DIO within EOF, use a shared lock
+ */
+ if (iocb->ki_pos + iov_iter_count(from) <= i_size_read(inode))
+ ilock_flags |= BTRFS_ILOCK_SHARED;
+ else if (iocb->ki_flags & IOCB_NOWAIT)
+ return -EAGAIN;
+
+relock:
Huh? Why are you making it so EOF extending NOWAIT writes now fail? We are
still using ILOCK_TRY here, so we may still not block, am I missing something?
Thanks,
Josef
