From: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Subject: shmem: shmem_charge: verify max_block is not exceeded before inode update Patch series "userfaultfd: enable zeropage support for shmem". These patches enable support for UFFDIO_ZEROPAGE for shared memory. The first two patches are not strictly related to userfaultfd, they are just minor refactoring to reduce amount of code duplication. This patch (of 7): Currently we update inode and shmem_inode_info before verifying that used_blocks will not exceed max_blocks. In case it will, we undo the update. Let's switch the order and move the verification of the blocks count before the inode and shmem_inode_info update. Link: http://lkml.kernel.org/r/1497939652-16528-2-git-send-email-rppt@xxxxxxxxxxxxxxxxxx Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx> Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/shmem.c | 25 ++++++++++++------------- 1 file changed, 12 insertions(+), 13 deletions(-) diff -puN mm/shmem.c~shmem-shmem_charge-verify-max_block-is-not-exceeded-before-inode-update mm/shmem.c --- a/mm/shmem.c~shmem-shmem_charge-verify-max_block-is-not-exceeded-before-inode-update +++ a/mm/shmem.c @@ -266,6 +266,14 @@ bool shmem_charge(struct inode *inode, l if (shmem_acct_block(info->flags, pages)) return false; + + if (sbinfo->max_blocks) { + if (percpu_counter_compare(&sbinfo->used_blocks, + sbinfo->max_blocks - pages) > 0) + goto unacct; + percpu_counter_add(&sbinfo->used_blocks, pages); + } + spin_lock_irqsave(&info->lock, flags); info->alloced += pages; inode->i_blocks += pages * BLOCKS_PER_PAGE; @@ -273,20 +281,11 @@ bool shmem_charge(struct inode *inode, l spin_unlock_irqrestore(&info->lock, flags); inode->i_mapping->nrpages += pages; - if (!sbinfo->max_blocks) - return true; - if (percpu_counter_compare(&sbinfo->used_blocks, - sbinfo->max_blocks - pages) > 0) { - inode->i_mapping->nrpages -= pages; - spin_lock_irqsave(&info->lock, flags); - info->alloced -= pages; - shmem_recalc_inode(inode); - spin_unlock_irqrestore(&info->lock, flags); - shmem_unacct_blocks(info->flags, pages); - return false; - } - percpu_counter_add(&sbinfo->used_blocks, pages); return true; + +unacct: + shmem_unacct_blocks(info->flags, pages); + return false; } void shmem_uncharge(struct inode *inode, long pages) _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
