6.12-stable review patch. If anyone has any objections, please let me know.
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From: David Howells dhowells@redhat.com
[ Upstream commit 2e0658940d90a3dc130bb3b7f75bae9f4100e01f ]
Fix the updating of i_size, particularly in regard to the completion of DIO writes and especially async DIO writes by using a lock.
The bug is triggered occasionally by the generic/207 xfstest as it chucks a bunch of AIO DIO writes at the filesystem and then checks that fstat() returns a reasonable st_size as each completes.
The problem is that netfs is trying to do "if new_size > inode->i_size, update inode->i_size" sort of thing but without a lock around it.
This can be seen with cifs, but shouldn't be seen with kafs because kafs serialises modification ops on the client whereas cifs sends the requests to the server as they're generated and lets the server order them.
Fixes: 153a9961b551 ("netfs: Implement unbuffered/DIO write support") Signed-off-by: David Howells dhowells@redhat.com Link: https://lore.kernel.org/20250701163852.2171681-11-dhowells@redhat.com Reviewed-by: Paulo Alcantara (Red Hat) pc@manguebit.org cc: Steve French sfrench@samba.org cc: Paulo Alcantara pc@manguebit.org cc: linux-cifs@vger.kernel.org cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/netfs/buffered_write.c | 2 ++ fs/netfs/direct_write.c | 8 ++++++-- 2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c index b3910dfcb56d3..896d1d4219ed9 100644 --- a/fs/netfs/buffered_write.c +++ b/fs/netfs/buffered_write.c @@ -64,6 +64,7 @@ static void netfs_update_i_size(struct netfs_inode *ctx, struct inode *inode, return; }
+ spin_lock(&inode->i_lock); i_size_write(inode, pos); #if IS_ENABLED(CONFIG_FSCACHE) fscache_update_cookie(ctx->cache, NULL, &pos); @@ -77,6 +78,7 @@ static void netfs_update_i_size(struct netfs_inode *ctx, struct inode *inode, DIV_ROUND_UP(pos, SECTOR_SIZE), inode->i_blocks + add); } + spin_unlock(&inode->i_lock); }
/** diff --git a/fs/netfs/direct_write.c b/fs/netfs/direct_write.c index 26cf9c94deebb..8fbfaf71c154c 100644 --- a/fs/netfs/direct_write.c +++ b/fs/netfs/direct_write.c @@ -14,13 +14,17 @@ static void netfs_cleanup_dio_write(struct netfs_io_request *wreq) struct inode *inode = wreq->inode; unsigned long long end = wreq->start + wreq->transferred;
- if (!wreq->error && - i_size_read(inode) < end) { + if (wreq->error || end <= i_size_read(inode)) + return; + + spin_lock(&inode->i_lock); + if (end > i_size_read(inode)) { if (wreq->netfs_ops->update_i_size) wreq->netfs_ops->update_i_size(inode, end); else i_size_write(inode, end); } + spin_unlock(&inode->i_lock); }
/*