From fac47b43c760ea90e64b895dba60df0327be7775 Mon Sep 17 00:00:00 2001 From: Xiubo Li Date: Mon, 11 Jul 2022 12:11:21 +0800 Subject: netfs: do not unlock and put the folio twice check_write_begin() will unlock and put the folio when return non-zero. So we should avoid unlocking and putting it twice in netfs layer. Change the way ->check_write_begin() works in the following two ways: (1) Pass it a pointer to the folio pointer, allowing it to unlock and put the folio prior to doing the stuff it wants to do, provided it clears the folio pointer. (2) Change the return values such that 0 with folio pointer set means continue, 0 with folio pointer cleared means re-get and all error codes indicating an error (no special treatment for -EAGAIN). [ bagasdotme: use Sphinx code text syntax for *foliop pointer ] Cc: stable@vger.kernel.org Link: https://tracker.ceph.com/issues/56423 Link: https://lore.kernel.org/r/cf169f43-8ee7-8697-25da-0204d1b4343e@redhat.com Co-developed-by: David Howells Signed-off-by: Xiubo Li Signed-off-by: David Howells Signed-off-by: Bagas Sanjaya Signed-off-by: Ilya Dryomov --- fs/netfs/buffered_read.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) (limited to 'fs/netfs') diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c index 42f892c5712e..0ce535852151 100644 --- a/fs/netfs/buffered_read.c +++ b/fs/netfs/buffered_read.c @@ -319,8 +319,9 @@ zero_out: * conflicting writes once the folio is grabbed and locked. It is passed a * pointer to the fsdata cookie that gets returned to the VM to be passed to * write_end. It is permitted to sleep. It should return 0 if the request - * should go ahead; unlock the folio and return -EAGAIN to cause the folio to - * be regot; or return an error. + * should go ahead or it may return an error. It may also unlock and put the + * folio, provided it sets ``*foliop`` to NULL, in which case a return of 0 + * will cause the folio to be re-got and the process to be retried. * * The calling netfs must initialise a netfs context contiguous to the vfs * inode before calling this. @@ -348,13 +349,13 @@ retry: if (ctx->ops->check_write_begin) { /* Allow the netfs (eg. ceph) to flush conflicts. */ - ret = ctx->ops->check_write_begin(file, pos, len, folio, _fsdata); + ret = ctx->ops->check_write_begin(file, pos, len, &folio, _fsdata); if (ret < 0) { trace_netfs_failure(NULL, NULL, ret, netfs_fail_check_write_begin); - if (ret == -EAGAIN) - goto retry; goto error; } + if (!folio) + goto retry; } if (folio_test_uptodate(folio)) @@ -416,8 +417,10 @@ have_folio_no_wait: error_put: netfs_put_request(rreq, false, netfs_rreq_trace_put_failed); error: - folio_unlock(folio); - folio_put(folio); + if (folio) { + folio_unlock(folio); + folio_put(folio); + } _leave(" = %d", ret); return ret; } -- cgit v1.2.3