6.10-stable review patch. If anyone has any objections, please let me know.
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From: David Howells dhowells@redhat.com
[ Upstream commit e00e99ba6c6b8e5239e75cd6684a6827d93c39a2 ]
When a folio that is marked for streaming write (dirty, but not uptodate, with partial content specified in the private data) is written back, the folio is effectively switched to the blank state upon completion of the write. This means that if we want to read it in future, we need to reread the whole folio.
However, if the folio is above the zero_point position, when it is read back, it will just be cleared and the read skipped, leading to apparent local corruption.
Fix this by increasing the zero_point to the end of the dirty data in the folio when clearing the folio state after writeback. This is analogous to the folio having ->release_folio() called upon it.
This was causing the config.log generated by configuring a cpython tree on a cifs share to get corrupted because the scripts involved were appending text to the file in small pieces.
Fixes: 288ace2f57c9 ("netfs: New writeback implementation") Signed-off-by: David Howells dhowells@redhat.com Link: https://lore.kernel.org/r/563286.1724500613@warthog.procyon.org.uk cc: Steve French sfrench@samba.org cc: Paulo Alcantara pc@manguebit.com cc: Jeff Layton jlayton@kernel.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/write_collect.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/fs/netfs/write_collect.c b/fs/netfs/write_collect.c index 488147439fe0f..a2b697b4aa401 100644 --- a/fs/netfs/write_collect.c +++ b/fs/netfs/write_collect.c @@ -33,6 +33,7 @@ int netfs_folio_written_back(struct folio *folio) { enum netfs_folio_trace why = netfs_folio_trace_clear; + struct netfs_inode *ictx = netfs_inode(folio->mapping->host); struct netfs_folio *finfo; struct netfs_group *group = NULL; int gcount = 0; @@ -41,6 +42,12 @@ int netfs_folio_written_back(struct folio *folio) /* Streaming writes cannot be redirtied whilst under writeback, * so discard the streaming record. */ + unsigned long long fend; + + fend = folio_pos(folio) + finfo->dirty_offset + finfo->dirty_len; + if (fend > ictx->zero_point) + ictx->zero_point = fend; + folio_detach_private(folio); group = finfo->netfs_group; gcount++;