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| author | Hugh Dickins <hughd@google.com> | 2023-07-25 16:45:10 +0200 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2023-08-09 09:15:40 +0200 |
| commit | 509f006932de7556d48eaa7afcd02dcf1ca9a3e9 (patch) | |
| tree | 54b4f72158590dca8035163a57e807f4e1143258 /mm/khugepaged.c | |
| parent | de4c0e7ca8b526a82ff7e5ee5533787bb6d01724 (diff) | |
| download | lwn-509f006932de7556d48eaa7afcd02dcf1ca9a3e9.tar.gz lwn-509f006932de7556d48eaa7afcd02dcf1ca9a3e9.zip | |
shmem: fix quota lock nesting in huge hole handling
i_pages lock nests inside i_lock, but shmem_charge() and shmem_uncharge()
were being called from THP splitting or collapsing while i_pages lock was
held, and now go on to call dquot_alloc_block_nodirty() which takes
i_lock to update i_blocks.
We may well want to take i_lock out of this path later, in the non-quota
case even if it's left in the quota case (or perhaps use i_lock instead
of shmem's info->lock throughout); but don't get into that at this time.
Move the shmem_charge() and shmem_uncharge() calls out from under i_pages
lock, accounting the full batch of holes in a single call.
Still pass the pages argument to shmem_uncharge(), but it happens now to
be unused: shmem_recalc_inode() is designed to account for clean pages
freed behind shmem's back, so it gets the accounting right by itself;
then the later call to shmem_inode_unacct_blocks() led to imbalance
(that WARN_ON(inode->i_blocks) in shmem_evict_inode()).
Reported-by: syzbot+38ca19393fb3344f57e6@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/lkml/0000000000008e62f40600bfe080@google.com/
Reported-by: syzbot+440ff8cca06ee7a1d4db@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/lkml/00000000000076a7840600bfb6e8@google.com/
Signed-off-by: Hugh Dickins <hughd@google.com>
Tested-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Message-Id: <20230725144510.253763-8-cem@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'mm/khugepaged.c')
| -rw-r--r-- | mm/khugepaged.c | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 78c8d5d8b628..47d1d32c734f 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1955,10 +1955,6 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr, goto xa_locked; } } - if (!shmem_charge(mapping->host, 1)) { - result = SCAN_FAIL; - goto xa_locked; - } nr_none++; continue; } @@ -2145,8 +2141,13 @@ xa_unlocked: */ try_to_unmap_flush(); - if (result != SCAN_SUCCEED) + if (result == SCAN_SUCCEED && nr_none && + !shmem_charge(mapping->host, nr_none)) + result = SCAN_FAIL; + if (result != SCAN_SUCCEED) { + nr_none = 0; goto rollback; + } /* * The old pages are locked, so they won't change anymore. @@ -2283,8 +2284,8 @@ rollback: if (nr_none) { xas_lock_irq(&xas); mapping->nrpages -= nr_none; - shmem_uncharge(mapping->host, nr_none); xas_unlock_irq(&xas); + shmem_uncharge(mapping->host, nr_none); } list_for_each_entry_safe(page, tmp, &pagelist, lru) { |