From: jlayton@kernel.org To: Andrew Morton <akpm@linux-foundation.org>, Al Viro <viro@ZenIV.linux.org.uk>, Jan Kara <jack@suse.cz>, tytso@mit.edu, axboe@kernel.dk, mawilcox@microsoft.com, ross.zwisler@linux.intel.com, corbet@lwn.net, Chris Mason <clm@fb.com>, Josef Bacik <jbacik@fb.com>, David Sterba <dsterba@suse.com>, "Darrick J . Wong" <darrick.wong@oracle.com> Cc: Carlos Maiolino <cmaiolino@redhat.com>, Eryu Guan <eguan@redhat.com>, David Howells <dhowells@redhat.com>, Christoph Hellwig <hch@infradead.org>, Liu Bo <bo.li.liu@oracle.com>, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-block@vger.kernel.org Subject: [PATCH v8 07/18] mm: don't TestClearPageError in __filemap_fdatawait_range Date: Thu, 29 Jun 2017 09:19:43 -0400 [thread overview] Message-ID: <20170629131954.28733-8-jlayton@kernel.org> (raw) In-Reply-To: <20170629131954.28733-1-jlayton@kernel.org> From: Jeff Layton <jlayton@redhat.com> The -EIO returned here can end up overriding whatever error is marked in the address space, and be returned at fsync time, even when there is a more appropriate error stored in the mapping. Read errors are also sometimes tracked on a per-page level using PG_error. Suppose we have a read error on a page, and then that page is subsequently dirtied by overwriting the whole page. Writeback doesn't clear PG_error, so we can then end up successfully writing back that page and still return -EIO on fsync. Worse yet, PG_error is cleared during a sync() syscall, but the -EIO return from that is silently discarded. Any subsystem that is relying on PG_error to report errors during fsync can easily lose writeback errors due to this. All you need is a stray sync() call to wait for writeback to complete and you've lost the error. Since the handling of the PG_error flag is somewhat inconsistent across subsystems, let's just rely on marking the address space when there are writeback errors. Change the TestClearPageError call to ClearPageError, and make __filemap_fdatawait_range a void return function. Signed-off-by: Jeff Layton <jlayton@redhat.com> --- mm/filemap.c | 20 +++++--------------- 1 file changed, 5 insertions(+), 15 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 49bc9720fb00..eb99b5f23c61 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -386,17 +386,16 @@ int filemap_flush(struct address_space *mapping) } EXPORT_SYMBOL(filemap_flush); -static int __filemap_fdatawait_range(struct address_space *mapping, +static void __filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, loff_t end_byte) { pgoff_t index = start_byte >> PAGE_SHIFT; pgoff_t end = end_byte >> PAGE_SHIFT; struct pagevec pvec; int nr_pages; - int ret = 0; if (end_byte < start_byte) - goto out; + return; pagevec_init(&pvec, 0); while ((index <= end) && @@ -413,14 +412,11 @@ static int __filemap_fdatawait_range(struct address_space *mapping, continue; wait_on_page_writeback(page); - if (TestClearPageError(page)) - ret = -EIO; + ClearPageError(page); } pagevec_release(&pvec); cond_resched(); } -out: - return ret; } /** @@ -440,14 +436,8 @@ static int __filemap_fdatawait_range(struct address_space *mapping, int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, loff_t end_byte) { - int ret, ret2; - - ret = __filemap_fdatawait_range(mapping, start_byte, end_byte); - ret2 = filemap_check_errors(mapping); - if (!ret) - ret = ret2; - - return ret; + __filemap_fdatawait_range(mapping, start_byte, end_byte); + return filemap_check_errors(mapping); } EXPORT_SYMBOL(filemap_fdatawait_range); -- 2.13.0
WARNING: multiple messages have this Message-ID (diff)
From: jlayton@kernel.org To: Andrew Morton <akpm@linux-foundation.org>, Al Viro <viro@ZenIV.linux.org.uk>, Jan Kara <jack@suse.cz>, tytso@mit.edu, axboe@kernel.dk, mawilcox@microsoft.com, ross.zwisler@linux.intel.com, corbet@lwn.net, Chris Mason <clm@fb.com>, Josef Bacik <jbacik@fb.com>, David Sterba <dsterba@suse.com>, "Darrick J . Wong" <darrick.wong@oracle.com> Cc: Carlos Maiolino <cmaiolino@redhat.com>, Eryu Guan <eguan@redhat.com>, David Howells <dhowells@redhat.com>, Christoph Hellwig <hch@infradead.org>, Liu Bo <bo.li.liu@oracle.com>, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-block@vger.kernel.org Subject: [PATCH v8 07/18] mm: don't TestClearPageError in __filemap_fdatawait_range Date: Thu, 29 Jun 2017 09:19:43 -0400 [thread overview] Message-ID: <20170629131954.28733-8-jlayton@kernel.org> (raw) In-Reply-To: <20170629131954.28733-1-jlayton@kernel.org> From: Jeff Layton <jlayton@redhat.com> The -EIO returned here can end up overriding whatever error is marked in the address space, and be returned at fsync time, even when there is a more appropriate error stored in the mapping. Read errors are also sometimes tracked on a per-page level using PG_error. Suppose we have a read error on a page, and then that page is subsequently dirtied by overwriting the whole page. Writeback doesn't clear PG_error, so we can then end up successfully writing back that page and still return -EIO on fsync. Worse yet, PG_error is cleared during a sync() syscall, but the -EIO return from that is silently discarded. Any subsystem that is relying on PG_error to report errors during fsync can easily lose writeback errors due to this. All you need is a stray sync() call to wait for writeback to complete and you've lost the error. Since the handling of the PG_error flag is somewhat inconsistent across subsystems, let's just rely on marking the address space when there are writeback errors. Change the TestClearPageError call to ClearPageError, and make __filemap_fdatawait_range a void return function. Signed-off-by: Jeff Layton <jlayton@redhat.com> --- mm/filemap.c | 20 +++++--------------- 1 file changed, 5 insertions(+), 15 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 49bc9720fb00..eb99b5f23c61 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -386,17 +386,16 @@ int filemap_flush(struct address_space *mapping) } EXPORT_SYMBOL(filemap_flush); -static int __filemap_fdatawait_range(struct address_space *mapping, +static void __filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, loff_t end_byte) { pgoff_t index = start_byte >> PAGE_SHIFT; pgoff_t end = end_byte >> PAGE_SHIFT; struct pagevec pvec; int nr_pages; - int ret = 0; if (end_byte < start_byte) - goto out; + return; pagevec_init(&pvec, 0); while ((index <= end) && @@ -413,14 +412,11 @@ static int __filemap_fdatawait_range(struct address_space *mapping, continue; wait_on_page_writeback(page); - if (TestClearPageError(page)) - ret = -EIO; + ClearPageError(page); } pagevec_release(&pvec); cond_resched(); } -out: - return ret; } /** @@ -440,14 +436,8 @@ static int __filemap_fdatawait_range(struct address_space *mapping, int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, loff_t end_byte) { - int ret, ret2; - - ret = __filemap_fdatawait_range(mapping, start_byte, end_byte); - ret2 = filemap_check_errors(mapping); - if (!ret) - ret = ret2; - - return ret; + __filemap_fdatawait_range(mapping, start_byte, end_byte); + return filemap_check_errors(mapping); } EXPORT_SYMBOL(filemap_fdatawait_range); -- 2.13.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-06-29 13:19 UTC|newest] Thread overview: 90+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-06-29 13:19 [PATCH v8 00/18] fs: enhanced writeback error reporting with errseq_t (pile #1) jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 13:19 ` [PATCH v8 01/18] fs: remove call_fsync helper function jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 13:19 ` [PATCH v8 02/18] buffer: use mapping_set_error instead of setting the flag jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 13:19 ` [PATCH v8 03/18] fs: check for writeback errors after syncing out buffers in generic_file_fsync jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 14:19 ` Christoph Hellwig 2017-06-29 14:19 ` Christoph Hellwig 2017-06-29 20:17 ` Jeff Layton 2017-06-29 20:17 ` Jeff Layton 2017-06-29 20:17 ` Jeff Layton 2017-06-29 20:17 ` Jeff Layton 2017-06-29 13:19 ` [PATCH v8 04/18] buffer: set errors in mapping at the time that the error occurs jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 13:19 ` [PATCH v8 05/18] jbd2: don't clear and reset errors after waiting on writeback jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 13:19 ` [PATCH v8 06/18] mm: clear AS_EIO/AS_ENOSPC when writeback initiation fails jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 13:19 ` jlayton [this message] 2017-06-29 13:19 ` [PATCH v8 07/18] mm: don't TestClearPageError in __filemap_fdatawait_range jlayton 2017-06-29 13:19 ` [PATCH v8 08/18] mm: clean up error handling in write_one_page jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 13:19 ` [PATCH v8 09/18] lib: add errseq_t type and infrastructure for handling it jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 13:19 ` [PATCH v8 10/18] fs: new infrastructure for writeback error handling and reporting jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 13:45 ` Jeff Layton 2017-06-29 13:45 ` Jeff Layton 2017-06-29 13:45 ` Jeff Layton 2017-06-29 13:45 ` Jeff Layton 2017-06-29 17:52 ` Jeff Layton 2017-06-29 17:52 ` Jeff Layton 2017-06-29 17:52 ` Jeff Layton 2017-06-29 17:52 ` Jeff Layton 2017-06-29 13:19 ` [PATCH v8 11/18] mm: set both AS_EIO/AS_ENOSPC and errseq_t in mapping_set_error jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 13:19 ` [PATCH v8 12/18] Documentation: flesh out the section in vfs.txt on storing and reporting writeback errors jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 17:11 ` Darrick J. Wong 2017-06-29 17:11 ` Darrick J. Wong 2017-06-29 18:13 ` Jeff Layton 2017-06-29 18:13 ` Jeff Layton 2017-06-29 18:13 ` Jeff Layton 2017-06-29 18:13 ` Jeff Layton 2017-06-29 18:21 ` Matthew Wilcox 2017-06-29 18:21 ` Matthew Wilcox 2017-06-29 18:21 ` Matthew Wilcox 2017-06-29 20:42 ` Jeff Layton 2017-06-29 20:42 ` Jeff Layton 2017-06-29 20:42 ` Jeff Layton 2017-06-29 20:42 ` Jeff Layton 2017-06-29 20:42 ` Jeff Layton 2017-06-29 13:19 ` [PATCH v8 13/18] dax: set errors in mapping when writeback fails jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 13:19 ` [PATCH v8 14/18] block: convert to errseq_t based writeback error tracking jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 14:18 ` Christoph Hellwig 2017-06-29 14:18 ` Christoph Hellwig 2017-06-29 13:19 ` [PATCH v8 15/18] fs: convert __generic_file_fsync to use errseq_t based reporting jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 13:19 ` [PATCH v8 16/18] ext4: use errseq_t based error handling for reporting data writeback errors jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 14:12 ` Christoph Hellwig 2017-06-29 14:12 ` Christoph Hellwig 2017-06-29 20:26 ` Jeff Layton 2017-06-29 20:26 ` Jeff Layton 2017-06-29 20:26 ` Jeff Layton 2017-06-29 20:26 ` Jeff Layton 2017-06-29 13:19 ` [PATCH v8 17/18] xfs: minimal conversion to errseq_t writeback error reporting jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 14:12 ` Christoph Hellwig 2017-06-29 14:12 ` Christoph Hellwig 2017-06-30 16:45 ` Jeff Layton 2017-06-30 16:45 ` Jeff Layton 2017-06-30 16:45 ` Jeff Layton 2017-06-30 16:45 ` Jeff Layton 2017-06-30 16:49 ` Christoph Hellwig 2017-06-30 16:49 ` Christoph Hellwig 2017-06-29 17:13 ` Darrick J. Wong 2017-06-29 17:13 ` Darrick J. Wong 2017-06-29 13:19 ` [PATCH v8 18/18] btrfs: minimal conversion to errseq_t writeback error reporting on fsync jlayton 2017-06-29 13:19 ` jlayton 2017-06-29 14:17 ` Christoph Hellwig 2017-06-29 14:17 ` Christoph Hellwig 2017-06-29 20:32 ` Jeff Layton 2017-06-29 20:32 ` Jeff Layton 2017-06-29 20:32 ` Jeff Layton 2017-06-29 20:32 ` Jeff Layton
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