From: "Darrick J. Wong" djwong@kernel.org
stable inclusion from stable-v5.10.141 commit 72a259bdd50dd6646a88e29fc769e50377e06d57 category: bugfix bugzilla: 188251,https://gitee.com/openeuler/kernel/issues/I685FC CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit 0baa2657dc4d79202148be79a3dc36c35f425060 upstream.
Nowadays, xfs_mod_fdblocks will always choose to fill the reserve pool with freed blocks before adding to fdblocks. Therefore, we can change the behavior of xfs_reserve_blocks slightly -- setting the target size of the pool should always succeed, since a deficiency will eventually be made up as blocks get freed.
Signed-off-by: Darrick J. Wong djwong@kernel.org Reviewed-by: Dave Chinner dchinner@redhat.com Signed-off-by: Amir Goldstein amir73il@gmail.com Acked-by: Darrick J. Wong djwong@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: yangerkun yangerkun@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Signed-off-by: Jialin Zhang zhangjialin11@huawei.com --- fs/xfs/xfs_fsops.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c index 3209e77ef84a..e555a8bbdbd7 100644 --- a/fs/xfs/xfs_fsops.c +++ b/fs/xfs/xfs_fsops.c @@ -378,11 +378,14 @@ xfs_reserve_blocks( * The code below estimates how many blocks it can request from * fdblocks to stash in the reserve pool. This is a classic TOCTOU * race since fdblocks updates are not always coordinated via - * m_sb_lock. + * m_sb_lock. Set the reserve size even if there's not enough free + * space to fill it because mod_fdblocks will refill an undersized + * reserve when it can. */ free = percpu_counter_sum(&mp->m_fdblocks) - xfs_fdblocks_unavailable(mp); delta = request - mp->m_resblks; + mp->m_resblks = request; if (delta > 0 && free > 0) { /* * We'll either succeed in getting space from the free block @@ -399,10 +402,8 @@ xfs_reserve_blocks( * Update the reserve counters if blocks have been successfully * allocated. */ - if (!error) { - mp->m_resblks += fdblks_delta; + if (!error) mp->m_resblks_avail += fdblks_delta; - } } out: if (outval) {