From patchwork Mon Jun 1 15:22:51 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chandan Rajendra X-Patchwork-Id: 6523491 Return-Path: X-Original-To: patchwork-linux-btrfs@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 46DF1C0020 for ; Mon, 1 Jun 2015 15:26:20 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id EB79420489 for ; Mon, 1 Jun 2015 15:26:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6308520481 for ; Mon, 1 Jun 2015 15:26:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753454AbbFAP0M (ORCPT ); Mon, 1 Jun 2015 11:26:12 -0400 Received: from e23smtp09.au.ibm.com ([202.81.31.142]:48277 "EHLO e23smtp09.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753402AbbFAP0I (ORCPT ); Mon, 1 Jun 2015 11:26:08 -0400 Received: from /spool/local by e23smtp09.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Tue, 2 Jun 2015 01:26:05 +1000 Received: from d23relay07.au.ibm.com (d23relay07.au.ibm.com [9.190.26.37]) by d23dlp02.au.ibm.com (Postfix) with ESMTP id 4D4BA2BB0040 for ; Tue, 2 Jun 2015 01:26:05 +1000 (EST) Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.235.139]) by d23relay07.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t51FOgXc41615576 for ; Tue, 2 Jun 2015 01:24:50 +1000 Received: from d23av04.au.ibm.com (localhost [127.0.0.1]) by d23av04.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t51FOHF3027849 for ; Tue, 2 Jun 2015 01:24:18 +1000 Received: from localhost.in.ibm.com ([9.124.217.22]) by d23av04.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVin) with ESMTP id t51FNTXF026813; Tue, 2 Jun 2015 01:24:15 +1000 From: Chandan Rajendra To: clm@fb.com, jbacik@fb.com, dsterba@suse.cz, bo.li.liu@oracle.com Cc: Chandan Rajendra , linux-btrfs@vger.kernel.org, chandan@mykolab.com Subject: [RFC PATCH V11 16/21] Btrfs: subpagesize-blocksize: Prevent writes to an extent buffer when PG_writeback flag is set. Date: Mon, 1 Jun 2015 20:52:51 +0530 Message-Id: <1433172176-8742-17-git-send-email-chandan@linux.vnet.ibm.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1433172176-8742-1-git-send-email-chandan@linux.vnet.ibm.com> References: <1433172176-8742-1-git-send-email-chandan@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15060115-0033-0000-0000-00000197240C Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP In non-subpagesize-blocksize scenario, BTRFS_HEADER_FLAG_WRITTEN flag prevents Btrfs code from writing into an extent buffer whose pages are under writeback. This facility isn't sufficient for achieving the same in subpagesize-blocksize scenario, since we have more than one extent buffer mapped to a page. Hence this patch adds a new flag (i.e. EXTENT_BUFFER_HEAD_WRITEBACK) and corresponding code to track the writeback status of the page and to prevent writes to any of the extent buffers mapped to the page while writeback is going on. Signed-off-by: Chandan Rajendra --- fs/btrfs/ctree.c | 21 ++++++- fs/btrfs/extent-tree.c | 11 ++++ fs/btrfs/extent_io.c | 150 ++++++++++++++++++++++++++++++++++++++++--------- fs/btrfs/extent_io.h | 1 + 4 files changed, 155 insertions(+), 28 deletions(-) diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index b28f14d..ba6fbb0 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -1535,6 +1535,7 @@ noinline int btrfs_cow_block(struct btrfs_trans_handle *trans, struct extent_buffer *parent, int parent_slot, struct extent_buffer **cow_ret) { + struct extent_buffer_head *ebh = eb_head(buf); u64 search_start; int ret; @@ -1548,6 +1549,14 @@ noinline int btrfs_cow_block(struct btrfs_trans_handle *trans, trans->transid, root->fs_info->generation); if (!should_cow_block(trans, root, buf)) { + if (test_bit(EXTENT_BUFFER_HEAD_WRITEBACK, &ebh->bflags)) { + if (parent) + btrfs_set_lock_blocking(parent); + btrfs_set_lock_blocking(buf); + wait_on_bit_io(&ebh->bflags, + EXTENT_BUFFER_HEAD_WRITEBACK, + TASK_UNINTERRUPTIBLE); + } *cow_ret = buf; return 0; } @@ -2665,6 +2674,7 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root *root, struct btrfs_key *key, struct btrfs_path *p, int ins_len, int cow) { + struct extent_buffer_head *ebh; struct extent_buffer *b; int slot; int ret; @@ -2767,8 +2777,17 @@ again: * then we don't want to set the path blocking, * so we test it here */ - if (!should_cow_block(trans, root, b)) + if (!should_cow_block(trans, root, b)) { + ebh = eb_head(b); + if (test_bit(EXTENT_BUFFER_HEAD_WRITEBACK, + &ebh->bflags)) { + btrfs_set_path_blocking(p); + wait_on_bit_io(&ebh->bflags, + EXTENT_BUFFER_HEAD_WRITEBACK, + TASK_UNINTERRUPTIBLE); + } goto cow_done; + } /* * must have write locks on this node and the diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index b93a922..fc324b8 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -7435,14 +7435,25 @@ static struct extent_buffer * btrfs_init_new_buffer(struct btrfs_trans_handle *trans, struct btrfs_root *root, u64 bytenr, int level) { + struct extent_buffer_head *ebh; struct extent_buffer *buf; buf = btrfs_find_create_tree_block(root, bytenr); if (!buf) return ERR_PTR(-ENOMEM); + + ebh = eb_head(buf); btrfs_set_header_generation(buf, trans->transid); btrfs_set_buffer_lockdep_class(root->root_key.objectid, buf, level); btrfs_tree_lock(buf); + + if (test_bit(EXTENT_BUFFER_HEAD_WRITEBACK, + &ebh->bflags)) { + btrfs_set_lock_blocking(buf); + wait_on_bit_io(&ebh->bflags, EXTENT_BUFFER_HEAD_WRITEBACK, + TASK_UNINTERRUPTIBLE); + } + clean_tree_block(trans, root->fs_info, buf); clear_bit(EXTENT_BUFFER_STALE, &buf->ebflags); diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 55f900a..1ae1059 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -3638,6 +3638,52 @@ void wait_on_extent_buffer_writeback(struct extent_buffer *eb) TASK_UNINTERRUPTIBLE); } +static void lock_extent_buffers(struct extent_buffer_head *ebh, + struct extent_page_data *epd) +{ + struct extent_buffer *locked_eb = NULL; + struct extent_buffer *eb; +again: + eb = &ebh->eb; + do { + if (eb == locked_eb) + continue; + + if (!btrfs_try_tree_write_lock(eb)) + goto backoff; + + } while ((eb = eb->eb_next) != NULL); + + return; + +backoff: + if (locked_eb && (locked_eb->start > eb->start)) + btrfs_tree_unlock(locked_eb); + + locked_eb = eb; + + eb = &ebh->eb; + while (eb != locked_eb) { + btrfs_tree_unlock(eb); + eb = eb->eb_next; + } + + flush_write_bio(epd); + + btrfs_tree_lock(locked_eb); + + goto again; +} + +static void unlock_extent_buffers(struct extent_buffer_head *ebh) +{ + struct extent_buffer *eb = &ebh->eb; + + do { + btrfs_tree_unlock(eb); + } while ((eb = eb->eb_next) != NULL); +} + static void lock_extent_buffer_pages(struct extent_buffer_head *ebh, struct extent_page_data *epd) { @@ -3657,21 +3703,17 @@ static void lock_extent_buffer_pages(struct extent_buffer_head *ebh, } static int noinline_for_stack -lock_extent_buffer_for_io(struct extent_buffer *eb, +mark_extent_buffer_writeback(struct extent_buffer *eb, struct btrfs_fs_info *fs_info, struct extent_page_data *epd) { + struct extent_buffer_head *ebh = eb_head(eb); + struct extent_buffer *cur; int dirty; int ret = 0; - if (!btrfs_try_tree_write_lock(eb)) { - flush_write_bio(epd); - btrfs_tree_lock(eb); - } - if (test_bit(EXTENT_BUFFER_WRITEBACK, &eb->ebflags)) { dirty = test_bit(EXTENT_BUFFER_DIRTY, &eb->ebflags); - btrfs_tree_unlock(eb); if (!epd->sync_io) { if (!dirty) return 1; @@ -3679,15 +3721,23 @@ lock_extent_buffer_for_io(struct extent_buffer *eb, return 2; } + cur = &ebh->eb; + do { + btrfs_set_lock_blocking(cur); + } while ((cur = cur->eb_next) != NULL); + flush_write_bio(epd); while (1) { wait_on_extent_buffer_writeback(eb); - btrfs_tree_lock(eb); if (!test_bit(EXTENT_BUFFER_WRITEBACK, &eb->ebflags)) break; - btrfs_tree_unlock(eb); } + + cur = &ebh->eb; + do { + btrfs_clear_lock_blocking(cur); + } while ((cur = cur->eb_next) != NULL); } /* @@ -3695,22 +3745,20 @@ lock_extent_buffer_for_io(struct extent_buffer *eb, * under IO since we can end up having no IO bits set for a short period * of time. */ - spin_lock(&eb_head(eb)->refs_lock); + spin_lock(&ebh->refs_lock); if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &eb->ebflags)) { set_bit(EXTENT_BUFFER_WRITEBACK, &eb->ebflags); - spin_unlock(&eb_head(eb)->refs_lock); + spin_unlock(&ebh->refs_lock); btrfs_set_header_flag(eb, BTRFS_HEADER_FLAG_WRITTEN); __percpu_counter_add(&fs_info->dirty_metadata_bytes, -eb->len, fs_info->dirty_metadata_batch); ret = 0; } else { - spin_unlock(&eb_head(eb)->refs_lock); + spin_unlock(&ebh->refs_lock); ret = 1; } - btrfs_tree_unlock(eb); - return ret; } @@ -3856,8 +3904,8 @@ static void set_btree_ioerr(struct extent_buffer *eb, struct page *page) static void end_bio_subpagesize_blocksize_ebh_writepage(struct bio *bio, int err) { - struct bio_vec *bvec; struct extent_buffer *eb; + struct bio_vec *bvec; int i, done; bio_for_each_segment_all(bvec, bio, i) { @@ -3887,6 +3935,15 @@ static void end_bio_subpagesize_blocksize_ebh_writepage(struct bio *bio, int err end_extent_buffer_writeback(eb); + if (done) { + struct extent_buffer_head *ebh = eb_head(eb); + + clear_bit(EXTENT_BUFFER_HEAD_WRITEBACK, + &ebh->bflags); + smp_mb__after_atomic(); + wake_up_bit(&ebh->bflags, + EXTENT_BUFFER_HEAD_WRITEBACK); + } } while ((eb = eb->eb_next) != NULL); } @@ -3896,6 +3953,7 @@ static void end_bio_subpagesize_blocksize_ebh_writepage(struct bio *bio, int err static void end_bio_regular_ebh_writepage(struct bio *bio, int err) { + struct extent_buffer_head *ebh; struct extent_buffer *eb; struct bio_vec *bvec; int i, done; @@ -3906,7 +3964,9 @@ static void end_bio_regular_ebh_writepage(struct bio *bio, int err) eb = (struct extent_buffer *)page->private; BUG_ON(!eb); - done = atomic_dec_and_test(&eb_head(eb)->io_bvecs); + ebh = eb_head(eb); + + done = atomic_dec_and_test(&ebh->io_bvecs); if (err || test_bit(EXTENT_BUFFER_WRITE_ERR, &eb->ebflags)) { ClearPageUptodate(page); @@ -3919,6 +3979,10 @@ static void end_bio_regular_ebh_writepage(struct bio *bio, int err) continue; end_extent_buffer_writeback(eb); + + clear_bit(EXTENT_BUFFER_HEAD_WRITEBACK, &ebh->bflags); + smp_mb__after_atomic(); + wake_up_bit(&ebh->bflags, EXTENT_BUFFER_HEAD_WRITEBACK); } bio_put(bio); @@ -3960,8 +4024,14 @@ write_regular_ebh(struct extent_buffer_head *ebh, set_btree_ioerr(eb, p); end_page_writeback(p); if (atomic_sub_and_test(num_pages - i, - &eb_head(eb)->io_bvecs)) + &ebh->io_bvecs)) { end_extent_buffer_writeback(eb); + clear_bit(EXTENT_BUFFER_HEAD_WRITEBACK, + &ebh->bflags); + smp_mb__after_atomic(); + wake_up_bit(&ebh->bflags, + EXTENT_BUFFER_HEAD_WRITEBACK); + } ret = -EIO; break; } @@ -3995,6 +4065,7 @@ static int write_subpagesize_blocksize_ebh(struct extent_buffer_head *ebh, unsigned long i; unsigned long bio_flags = 0; int rw = (epd->sync_io ? WRITE_SYNC : WRITE) | REQ_META; + int nr_eb_submitted = 0; int ret = 0, err = 0; eb = &ebh->eb; @@ -4007,7 +4078,7 @@ static int write_subpagesize_blocksize_ebh(struct extent_buffer_head *ebh, continue; clear_bit(EXTENT_BUFFER_WRITE_ERR, &eb->ebflags); - atomic_inc(&eb_head(eb)->io_bvecs); + atomic_inc(&ebh->io_bvecs); if (btrfs_header_owner(eb) == BTRFS_TREE_LOG_OBJECTID) bio_flags = EXTENT_BIO_TREE_LOG; @@ -4025,6 +4096,8 @@ static int write_subpagesize_blocksize_ebh(struct extent_buffer_head *ebh, atomic_dec(&eb_head(eb)->io_bvecs); end_extent_buffer_writeback(eb); err = -EIO; + } else { + ++nr_eb_submitted; } } while ((eb = eb->eb_next) != NULL); @@ -4032,6 +4105,12 @@ static int write_subpagesize_blocksize_ebh(struct extent_buffer_head *ebh, update_nr_written(p, wbc, 1); } + if (!nr_eb_submitted) { + clear_bit(EXTENT_BUFFER_HEAD_WRITEBACK, &ebh->bflags); + smp_mb__after_atomic(); + wake_up_bit(&ebh->bflags, EXTENT_BUFFER_HEAD_WRITEBACK); + } + unlock_page(p); return ret; @@ -4143,24 +4222,31 @@ retry: j = 0; ebs_to_write = dirty_ebs = 0; + + lock_extent_buffers(ebh, &epd); + + set_bit(EXTENT_BUFFER_HEAD_WRITEBACK, &ebh->bflags); + eb = &ebh->eb; do { BUG_ON(j >= BITS_PER_LONG); - ret = lock_extent_buffer_for_io(eb, fs_info, &epd); + ret = mark_extent_buffer_writeback(eb, fs_info, + &epd); switch (ret) { case 0: /* - EXTENT_BUFFER_DIRTY was set and we were able to - clear it. + EXTENT_BUFFER_DIRTY was set and we were + able to clear it. */ set_bit(j, &ebs_to_write); break; case 2: /* - EXTENT_BUFFER_DIRTY was set, but we were unable - to clear EXTENT_BUFFER_WRITEBACK that was set - before we got the extent buffer locked. + EXTENT_BUFFER_DIRTY was set, but we were + unable to clear EXTENT_BUFFER_WRITEBACK + that was set before we got the extent + buffer locked. */ set_bit(j, &dirty_ebs); default: @@ -4174,22 +4260,32 @@ retry: ret = 0; + unlock_extent_buffers(ebh); + if (!ebs_to_write) { + clear_bit(EXTENT_BUFFER_HEAD_WRITEBACK, + &ebh->bflags); + smp_mb__after_atomic(); + wake_up_bit(&ebh->bflags, + EXTENT_BUFFER_HEAD_WRITEBACK); free_extent_buffer(&ebh->eb); continue; } /* - Now that we know that atleast one of the extent buffer + Now that we know that atleast one of the extent buffers belonging to the extent buffer head must be written to the disk, lock the extent_buffer_head's pages. */ lock_extent_buffer_pages(ebh, &epd); if (ebh->eb.len < PAGE_CACHE_SIZE) { - ret = write_subpagesize_blocksize_ebh(ebh, fs_info, wbc, &epd, ebs_to_write); + ret = write_subpagesize_blocksize_ebh(ebh, fs_info, + wbc, &epd, + ebs_to_write); if (dirty_ebs) { - redirty_extent_buffer_pages_for_writepage(&ebh->eb, wbc); + redirty_extent_buffer_pages_for_writepage(&ebh->eb, + wbc); } } else { ret = write_regular_ebh(ebh, fs_info, wbc, &epd); diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h index c629e53..cbc7d73 100644 --- a/fs/btrfs/extent_io.h +++ b/fs/btrfs/extent_io.h @@ -42,6 +42,7 @@ #define EXTENT_BUFFER_DUMMY 9 #define EXTENT_BUFFER_IN_TREE 10 #define EXTENT_BUFFER_WRITE_ERR 11 /* write IO error */ +#define EXTENT_BUFFER_HEAD_WRITEBACK 12 /* these are flags for extent_clear_unlock_delalloc */ #define PAGE_UNLOCK (1 << 0)