From patchwork Wed Nov 20 21:51:03 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dennis Zhou X-Patchwork-Id: 11254861 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 1F9A96C1 for ; Wed, 20 Nov 2019 21:51:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EAB6620709 for ; Wed, 20 Nov 2019 21:51:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574286695; bh=9hwfSkuDGvWUAsbOdX4ItVcaJjsb+65iiYjLsyffDNQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:In-Reply-To: References:List-ID:From; b=BSs+JPB8PjNH5ajCQHn8w6oBOphyFAudAhJUJ3WUWOTHnYVoz1tNYwegnZSaUmQtA mbbNwZhT5n5UsRysV0QKW0onG+9fMjK9NTx9R0fRomxaQw8rY/ayXqzeyI1vdPZv8Y d5oBLYs0gnnNdKg06MnaHEgfdT0iC9z43ep12OLo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726840AbfKTVvd (ORCPT ); Wed, 20 Nov 2019 16:51:33 -0500 Received: from mail-qv1-f67.google.com ([209.85.219.67]:36079 "EHLO mail-qv1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726822AbfKTVvd (ORCPT ); Wed, 20 Nov 2019 16:51:33 -0500 Received: by mail-qv1-f67.google.com with SMTP id cv8so580784qvb.3 for ; Wed, 20 Nov 2019 13:51:32 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:in-reply-to:references; bh=JbS6Xnh6/UEk+qphSqVZ3EdK4Ri8tUYlmlPZnPj+vhs=; b=eNx5XmVsIMpsl2a/PadR7ccsaFpI3rFpTe/bJDkso+PR7n3olCrmjOmQxGFPxqVrLQ 4FrjCYGX+cnQzZrfvkZAzJ/nvNcYTdPT+s5V/7T8ysr2gtJAlp/X877pwSkFsn1+TOd7 ZcjbdDLbjDwSoXm4Ztqqt0JOD0Ya1OY08wjspXE1EFbhauCHwFWA8BAKGwkILpETjc1f J9JckLAUFWyn/QFKwcit2eXbBwfodA2b3BSOxD/vAtIMmbq+qKMhbsb+cFkmyPh7oeNp /OxPeV+bcyb5GSphrya/o2EouE0GWq9PSjPEFfmMetmBnCcM5RrclDSsPqMtuh1Wrpa6 o7Vw== X-Gm-Message-State: APjAAAV5Za4PbheqVIoRXQUjMDCtnfCpYIFa9FDONmwAE9b/D6EYuWMx EIaDRrKiEa0e6TGabEyVBVs= X-Google-Smtp-Source: APXvYqybgFCOUq+DgA1uOFjes5ovKCvZVXGMwkcGeBNk9o/YbO3RrZeCVPwNjPLJmLw4TxNa8neuCw== X-Received: by 2002:a0c:9314:: with SMTP id d20mr5010304qvd.28.1574286692105; Wed, 20 Nov 2019 13:51:32 -0800 (PST) Received: from dennisz-mbp.thefacebook.com ([163.114.130.128]) by smtp.gmail.com with ESMTPSA id t16sm303820qkm.73.2019.11.20.13.51.30 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 20 Nov 2019 13:51:30 -0800 (PST) From: Dennis Zhou To: David Sterba , Chris Mason , Josef Bacik , Omar Sandoval Cc: kernel-team@fb.com, linux-btrfs@vger.kernel.org, Dennis Zhou Subject: [PATCH 04/22] btrfs: keep track of cleanliness of the bitmap Date: Wed, 20 Nov 2019 16:51:03 -0500 Message-Id: <06410c758182c36e3af04249721ded50d8f2c62f.1574282259.git.dennis@kernel.org> X-Mailer: git-send-email 2.13.5 In-Reply-To: References: In-Reply-To: References: Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org There is a cap in btrfs in the amount of free extents that a block group can have. When it surpasses that threshold, future extents are placed into bitmaps. Instead of keeping track of if a certain bit is trimmed or not in a second bitmap, keep track of the relative state of the bitmap. With async discard, trimming bitmaps becomes a more frequent operation. As a trade off with simplicity, we keep track of if discarding a bitmap is in progress. If we fully scan a bitmap and trim as necessary, the bitmap is marked clean. This has some caveats as the min block size may skip over regions deemed too small. But this should be a reasonable trade off rather than keeping a second bitmap and making allocation paths more complex. The downside is we may overtrim, but ideally the min block size should prevent us from doing that too often and getting stuck trimming pathological cases. BTRFS_TRIM_STATE_TRIMMING is added to indicate a bitmap is in the process of being trimmed. If additional free space is added to that bitmap, the bit is cleared. A bitmap will be marked BTRFS_TRIM_STATE_TRIMMED if the trimming code was able to reach the end of it and the former is still set. Signed-off-by: Dennis Zhou Reviewed-by: Josef Bacik --- fs/btrfs/free-space-cache.c | 89 +++++++++++++++++++++++++++++++++---- fs/btrfs/free-space-cache.h | 12 +++++ 2 files changed, 92 insertions(+), 9 deletions(-) diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c index 399c641440bc..946a7df33249 100644 --- a/fs/btrfs/free-space-cache.c +++ b/fs/btrfs/free-space-cache.c @@ -1979,11 +1979,18 @@ static noinline int remove_from_bitmap(struct btrfs_free_space_ctl *ctl, static u64 add_bytes_to_bitmap(struct btrfs_free_space_ctl *ctl, struct btrfs_free_space *info, u64 offset, - u64 bytes) + u64 bytes, enum btrfs_trim_state trim_state) { u64 bytes_to_set = 0; u64 end; + /* + * This is a tradeoff to make bitmap trim state minimal. We mark the + * whole bitmap untrimmed if at any point we add untrimmed regions. + */ + if (trim_state == BTRFS_TRIM_STATE_UNTRIMMED) + info->trim_state = BTRFS_TRIM_STATE_UNTRIMMED; + end = info->offset + (u64)(BITS_PER_BITMAP * ctl->unit); bytes_to_set = min(end - offset, bytes); @@ -2058,10 +2065,12 @@ static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl, struct btrfs_block_group *block_group = NULL; int added = 0; u64 bytes, offset, bytes_added; + enum btrfs_trim_state trim_state; int ret; bytes = info->bytes; offset = info->offset; + trim_state = info->trim_state; if (!ctl->op->use_bitmap(ctl, info)) return 0; @@ -2096,8 +2105,8 @@ static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl, } if (entry->offset == offset_to_bitmap(ctl, offset)) { - bytes_added = add_bytes_to_bitmap(ctl, entry, - offset, bytes); + bytes_added = add_bytes_to_bitmap(ctl, entry, offset, + bytes, trim_state); bytes -= bytes_added; offset += bytes_added; } @@ -2116,7 +2125,8 @@ static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl, goto new_bitmap; } - bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes); + bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes, + trim_state); bytes -= bytes_added; offset += bytes_added; added = 0; @@ -2150,6 +2160,7 @@ static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl, /* allocate the bitmap */ info->bitmap = kmem_cache_zalloc(btrfs_free_space_bitmap_cachep, GFP_NOFS); + info->trim_state = BTRFS_TRIM_STATE_TRIMMED; spin_lock(&ctl->tree_lock); if (!info->bitmap) { ret = -ENOMEM; @@ -3320,6 +3331,39 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group, return ret; } +/* + * If we break out of trimming a bitmap prematurely, we should reset the + * trimming bit. In a rather contrieved case, it's possible to race here so + * reset the state to BTRFS_TRIM_STATE_UNTRIMMED. + * + * start = start of bitmap + * end = near end of bitmap + * + * Thread 1: Thread 2: + * trim_bitmaps(start) + * trim_bitmaps(end) + * end_trimming_bitmap() + * reset_trimming_bitmap() + */ +static void reset_trimming_bitmap(struct btrfs_free_space_ctl *ctl, u64 offset) +{ + struct btrfs_free_space *entry; + + spin_lock(&ctl->tree_lock); + + entry = tree_search_offset(ctl, offset, 1, 0); + if (entry) + entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED; + + spin_unlock(&ctl->tree_lock); +} + +static void end_trimming_bitmap(struct btrfs_free_space *entry) +{ + if (btrfs_free_space_trimming_bitmap(entry)) + entry->trim_state = BTRFS_TRIM_STATE_TRIMMED; +} + static int trim_bitmaps(struct btrfs_block_group *block_group, u64 *total_trimmed, u64 start, u64 end, u64 minlen) { @@ -3344,16 +3388,33 @@ static int trim_bitmaps(struct btrfs_block_group *block_group, } entry = tree_search_offset(ctl, offset, 1, 0); - if (!entry) { + if (!entry || btrfs_free_space_trimmed(entry)) { spin_unlock(&ctl->tree_lock); mutex_unlock(&ctl->cache_writeout_mutex); next_bitmap = true; goto next; } + /* + * Async discard bitmap trimming begins at by setting the start + * to be key.objectid and the offset_to_bitmap() aligns to the + * start of the bitmap. This lets us know we are fully + * scanning the bitmap rather than only some portion of it. + */ + if (start == offset) + entry->trim_state = BTRFS_TRIM_STATE_TRIMMING; + bytes = minlen; ret2 = search_bitmap(ctl, entry, &start, &bytes, false); if (ret2 || start >= end) { + /* + * This keeps the invariant that all bytes are trimmed + * if BTRFS_TRIM_STATE_TRIMMED is set on a bitmap. + */ + if (ret2 && !minlen) + end_trimming_bitmap(entry); + else + entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED; spin_unlock(&ctl->tree_lock); mutex_unlock(&ctl->cache_writeout_mutex); next_bitmap = true; @@ -3362,6 +3423,7 @@ static int trim_bitmaps(struct btrfs_block_group *block_group, bytes = min(bytes, end - start); if (bytes < minlen) { + entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED; spin_unlock(&ctl->tree_lock); mutex_unlock(&ctl->cache_writeout_mutex); goto next; @@ -3379,18 +3441,21 @@ static int trim_bitmaps(struct btrfs_block_group *block_group, ret = do_trimming(block_group, total_trimmed, start, bytes, start, bytes, &trim_entry); - if (ret) + if (ret) { + reset_trimming_bitmap(ctl, offset); break; + } next: if (next_bitmap) { offset += BITS_PER_BITMAP * ctl->unit; + start = offset; } else { start += bytes; - if (start >= offset + BITS_PER_BITMAP * ctl->unit) - offset += BITS_PER_BITMAP * ctl->unit; } if (fatal_signal_pending(current)) { + if (start != offset) + reset_trimming_bitmap(ctl, offset); ret = -ERESTARTSYS; break; } @@ -3444,6 +3509,7 @@ void btrfs_put_block_group_trimming(struct btrfs_block_group *block_group) int btrfs_trim_block_group(struct btrfs_block_group *block_group, u64 *trimmed, u64 start, u64 end, u64 minlen) { + struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl; int ret; *trimmed = 0; @@ -3461,6 +3527,9 @@ int btrfs_trim_block_group(struct btrfs_block_group *block_group, goto out; ret = trim_bitmaps(block_group, trimmed, start, end, minlen); + /* If we ended in the middle of a bitmap, reset the trimming flag. */ + if (end % (BITS_PER_BITMAP * ctl->unit)) + reset_trimming_bitmap(ctl, offset_to_bitmap(ctl, end)); out: btrfs_put_block_group_trimming(block_group); return ret; @@ -3645,6 +3714,7 @@ int test_add_free_space_entry(struct btrfs_block_group *cache, struct btrfs_free_space_ctl *ctl = cache->free_space_ctl; struct btrfs_free_space *info = NULL, *bitmap_info; void *map = NULL; + enum btrfs_trim_state trim_state = BTRFS_TRIM_STATE_TRIMMED; u64 bytes_added; int ret; @@ -3686,7 +3756,8 @@ int test_add_free_space_entry(struct btrfs_block_group *cache, info = NULL; } - bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes); + bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes, + trim_state); bytes -= bytes_added; offset += bytes_added; diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h index 66c073f854dc..29d16f58b40b 100644 --- a/fs/btrfs/free-space-cache.h +++ b/fs/btrfs/free-space-cache.h @@ -8,10 +8,16 @@ /* * This is the trim state of an extent or bitmap. + * + * BTRFS_TRIM_STATE_TRIMMING is special and used to maintain the state of a + * bitmap as we may need several trims to fully trim a single bitmap entry. + * This is reset should any free space other than trimmed space is added to the + * bitmap. */ enum btrfs_trim_state { BTRFS_TRIM_STATE_UNTRIMMED, BTRFS_TRIM_STATE_TRIMMED, + BTRFS_TRIM_STATE_TRIMMING, }; struct btrfs_free_space { @@ -29,6 +35,12 @@ static inline bool btrfs_free_space_trimmed(struct btrfs_free_space *info) return (info->trim_state == BTRFS_TRIM_STATE_TRIMMED); } +static inline bool btrfs_free_space_trimming_bitmap( + struct btrfs_free_space *info) +{ + return (info->trim_state == BTRFS_TRIM_STATE_TRIMMING); +} + struct btrfs_free_space_ctl { spinlock_t tree_lock; struct rb_root free_space_offset;