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Tue, 26 Nov 2024 06:29:51 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id OOACOt9qRWeZUQAAD6G6ig (envelope-from ); Tue, 26 Nov 2024 06:29:51 +0000 From: Qu Wenruo To: linux-btrfs@vger.kernel.org Cc: stable@vger.kernel.org Subject: [PATCH 1/2] btrfs: handle btrfs_run_delalloc_range() errors correctly Date: Tue, 26 Nov 2024 16:59:23 +1030 Message-ID: <3d7d7a1151b3f3cc64dbf3a06d46dd08c5c86a8f.1732596971.git.wqu@suse.com> X-Mailer: git-send-email 2.47.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Rspamd-Queue-Id: 5C18F21153 X-Spam-Score: -3.01 X-Rspamd-Action: no action X-Spamd-Result: default: False [-3.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_CONTAINS_FROM(1.00)[]; R_MISSING_CHARSET(0.50)[]; R_DKIM_ALLOW(-0.20)[suse.com:s=susede1]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; FROM_HAS_DN(0.00)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; MIME_TRACE(0.00)[0:+]; RCVD_COUNT_TWO(0.00)[2]; FUZZY_BLOCKED(0.00)[rspamd.com]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TO_DN_NONE(0.00)[]; RCVD_TLS_ALL(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCPT_COUNT_TWO(0.00)[2]; DKIM_SIGNED(0.00)[suse.com:s=susede1]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; DKIM_TRACE(0.00)[suse.com:+] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Flag: NO X-Spam-Level: [BUG] There are several crash or hang during fstests runs with sectorsize < page size setup. It turns out that most of those hang happens after a btrfs_run_delalloc_range() failure (caused by -ENOSPC). The most common one is generic/750. The symptom are all related to ordered extent finishing, where we double account the target ordered extent. [CAUSE] Inside writepage_delalloc() if we hit an error from btrfs_run_delalloc_range(), we still need to unlock all the locked range, but that's the only error handling. If we have the following page layout with a 64K page size and 4K sector size: 0 4K 32K 40K 60K 64K |////| |////| |/////| Where |//| is the dirtied blocks inside the folio. Then we hit the following sequence: - Enter writepage_delalloc() for folio 0 - btrfs_run_delalloc_range() returned 0 for [0, 4K) And created regular COW ordered extent for range [0, 4K) - btrfs_run_delalloc_range() returned 0 for [32K, 40K) And created async extent for range [32K, 40K). This means the error handling will be done in another thread, we should not touch the range anymore. - btrfs_run_delalloc_range() failed with -ENOSPC for range [60K, 64K) In theory we should not fail since we should have reserved enough space at buffered write time, but let's ignore that rabbit hole and focus on the error handling. - Error handling in extent_writepage() Now we go to the done: tag, calling btrfs_mark_ordered_io_finished() for the whole folio range. This will find ranges [0, 4K) and [32K, 40K) to cleanup, for [0, 4K) it should be cleaned up, but for range [32K, 40K) it's asynchronously handled, the OE may have already been submitted. This will lead to the double account for range [32K, 40K) and crash the kernel. Unfortunately this bad error handling is from the very beginning of sector size < page size support. [FIX] Instead of relying on the btrfs_mark_ordered_io_finished() call to cleanup the whole folio range, record the last successfully ran delalloc range. And combined with bio_ctrl->submit_bitmap to properly clean up any newly created ordered extents. Since we have cleaned up the ordered extents in range, we should not rely on the btrfs_mark_ordered_io_finished() inside extent_writepage() anymore. By this, we should avoid double accounting during error handling. Cc: stable@vger.kernel.org # 5.15+ Signed-off-by: Qu Wenruo --- fs/btrfs/extent_io.c | 45 ++++++++++++++++++++++++++++++++++++-------- 1 file changed, 37 insertions(+), 8 deletions(-) diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 438974d4def4..0132c2b84d99 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -1145,11 +1145,13 @@ static bool find_next_delalloc_bitmap(struct folio *folio, * helper for extent_writepage(), doing all of the delayed allocation setup. * * This returns 1 if btrfs_run_delalloc_range function did all the work required - * to write the page (copy into inline extent). In this case the IO has - * been started and the page is already unlocked. + * to write the page (copy into inline extent or compression). In this case + * the IO has been started and we should no longer touch the page (may have + * already been unlocked). * * This returns 0 if all went well (page still locked) - * This returns < 0 if there were errors (page still locked) + * This returns < 0 if there were errors (page still locked), in this case any + * newly created delalloc range will be marked as error and finished. */ static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode, struct folio *folio, @@ -1167,6 +1169,12 @@ static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode, * last delalloc end. */ u64 last_delalloc_end = 0; + /* + * Save the last successfully ran delalloc range end (exclusive). + * This is for error handling to avoid ranges with ordered extent created + * but no IO will be submitted due to error. + */ + u64 last_finished = page_start; u64 delalloc_start = page_start; u64 delalloc_end = page_end; u64 delalloc_to_write = 0; @@ -1235,11 +1243,19 @@ static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode, found_len = last_delalloc_end + 1 - found_start; if (ret >= 0) { + /* + * Some delalloc range may be created by previous folios. + * Thus we still need to clean those range up during error + * handling. + */ + last_finished = found_start; /* No errors hit so far, run the current delalloc range. */ ret = btrfs_run_delalloc_range(inode, folio, found_start, found_start + found_len - 1, wbc); + if (ret >= 0) + last_finished = found_start + found_len; } else { /* * We've hit an error during previous delalloc range, @@ -1274,8 +1290,21 @@ static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode, delalloc_start = found_start + found_len; } - if (ret < 0) + /* + * It's possible we have some ordered extents created before we hit + * an error, cleanup non-async successfully created delalloc ranges. + */ + if (unlikely(ret < 0)) { + unsigned int bitmap_size = min( + (last_finished - page_start) >> fs_info->sectorsize_bits, + fs_info->sectors_per_page); + + for_each_set_bit(bit, &bio_ctrl->submit_bitmap, bitmap_size) + btrfs_mark_ordered_io_finished(inode, folio, + page_start + (bit << fs_info->sectorsize_bits), + fs_info->sectorsize, false); return ret; + } out: if (last_delalloc_end) delalloc_end = last_delalloc_end; @@ -1509,13 +1538,13 @@ static int extent_writepage(struct folio *folio, struct btrfs_bio_ctrl *bio_ctrl bio_ctrl->wbc->nr_to_write--; -done: - if (ret) { + if (ret) btrfs_mark_ordered_io_finished(BTRFS_I(inode), folio, page_start, PAGE_SIZE, !ret); - mapping_set_error(folio->mapping, ret); - } +done: + if (ret < 0) + mapping_set_error(folio->mapping, ret); /* * Only unlock ranges that are submitted. As there can be some async * submitted ranges inside the folio.