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Message-Id: <015bd57d5ff409cef6d452dffd4c140848ea5021.1589086820.git.riteshh@linux.ibm.com> Date: Sun, 10 May 2020 12:38:22 +0530 From: Ritesh Harjani <riteshh@...ux.ibm.com> To: linux-ext4@...r.kernel.org Cc: linux-fsdevel@...r.kernel.org, Jan Kara <jack@...e.com>, tytso@....edu, "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>, linux-kernel@...r.kernel.org, Ritesh Harjani <riteshh@...ux.ibm.com> Subject: [RFCv4 2/6] ext4: mballoc: Use ext4_lock_group() around calculations involving bb_free Currently while doing block allocation grp->bb_free may be getting modified if discard is happening in parallel. For e.g. consider a case where there are lot of threads who have preallocated lot of blocks and there is a thread which is trying to discard all of this group's PA. Now it could happen that we see all of those group's bb_free is zero and fail the allocation while there is sufficient space if we free up all the PA. So this patch takes the ext4_lock_group() around calculations involving grp->bb_free in ext4_mb_good_group() & ext4_mb_good_group_nolock() Signed-off-by: Ritesh Harjani <riteshh@...ux.ibm.com> --- fs/ext4/mballoc.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index da11a4a738bd..dcd05ff7c012 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -2138,9 +2138,11 @@ static int ext4_mb_good_group_nolock(struct ext4_allocation_context *ac, ext4_group_t group, int cr) { struct ext4_group_info *grp = ext4_get_group_info(ac->ac_sb, group); + struct super_block *sb = ac->ac_sb; ext4_grpblk_t free; int ret = 0; + ext4_lock_group(sb, group); free = grp->bb_free; if (free == 0) goto out; @@ -2148,6 +2150,7 @@ static int ext4_mb_good_group_nolock(struct ext4_allocation_context *ac, goto out; if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(grp))) goto out; + ext4_unlock_group(sb, group); /* We only do this if the grp has never been initialized */ if (unlikely(EXT4_MB_GRP_NEED_INIT(grp))) { @@ -2156,8 +2159,10 @@ static int ext4_mb_good_group_nolock(struct ext4_allocation_context *ac, return ret; } + ext4_lock_group(sb, group); ret = ext4_mb_good_group(ac, group, cr); out: + ext4_unlock_group(sb, group); return ret; } -- 2.21.0
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