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ntfs: avoid truncate and writeback deadlock

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ntfs_non_resident_attr_shrink() drops page-cache folios after freeing
clusters and truncating the runlist. The VFS truncate path calls it with
mrec_lock held. A folio writeback can need the same lock to resolve its
iomap mapping, so truncate can wait for writeback while writeback waits
for mrec_lock.

A hung-task call stack:

    truncate: mrec_lock -> truncate_inode_pages() -> folio lock/writeback

    writeback: folio lock/writeback -> ntfs_write_iomap_begin() ->
               mrec_lock

ntfs_setattr_size() already calls truncate_setsize() before
ntfs_truncate_vfs() acquires mrec_lock. Reuse that page-cache truncation
in the VFS path and skip the duplicate truncation under mrec_lock. Keep
the cleanup for internal attribute callers, which do not call
truncate_setsize(). This avoids synchronously flushing the whole
discarded tail while preserving page-cache correctness.

Fixes: 4e646ecd44 ("ntfs: drop stale page-cache when shrinking a non-resident attr")
Cc: stable@vger.kernel.org
Signed-off-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
This commit is contained in:
Hyunchul Lee 2026-09-15 00:19:15 +09:00 committed by Namjae Jeon
parent 67f27176e2
commit fca746064d
1 changed files with 7 additions and 4 deletions
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11
fs/ntfs/attrib.c
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@ -4234,12 +4234,14 @@ static int ntfs_attr_make_resident(struct ntfs_inode *ni, struct ntfs_attr_searc
* ntfs_non_resident_attr_shrink - shrink a non-resident, open ntfs attribute
* @ni: non-resident ntfs attribute to shrink
* @newsize: new size (in bytes) to which to shrink the attribute
* @pagecache_truncated: page cache was already truncated to @newsize
*
* Reduce the size of a non-resident, open ntfs attribute @na to @newsize bytes.
*/
static int ntfs_non_resident_attr_shrink(struct ntfs_inode *ni,
const s64 newsize,
struct ntfs_inode *locked_ni)
struct ntfs_inode *locked_ni,
bool pagecache_truncated)
{
struct ntfs_volume *vol;
struct ntfs_attr_search_ctx *ctx;
@ -4389,7 +4391,8 @@ static int ntfs_non_resident_attr_shrink(struct ntfs_inode *ni,
* later writeback map a vcn past the new allocation, which fails with
* -ENOENT and loses the write.
*/
truncate_inode_pages(VFS_I(ni)->i_mapping, newsize);
if (!pagecache_truncated)
truncate_inode_pages(VFS_I(ni)->i_mapping, newsize);
/* Update data size in the index. */
if (ni->type == AT_DATA && ni->name == AT_UNNAMED)
@ -4991,7 +4994,7 @@ int __ntfs_attr_truncate_vfs(struct ntfs_inode *ni, const s64 newsize,
up_write(&ni->runlist.lock);
} else
err = ntfs_non_resident_attr_shrink(
ni, newsize, NULL);
ni, newsize, NULL, true);
} else
err = ntfs_resident_attr_resize(ni, newsize, 0,
NVolDisableSparse(ni->vol) ?
@ -5104,7 +5107,7 @@ int ntfs_attr_truncate_i_locked(struct ntfs_inode *ni, const s64 newsize,
ni, newsize, 0, holes, locked_ni);
else
err = ntfs_non_resident_attr_shrink(
ni, newsize, locked_ni);
ni, newsize, locked_ni, false);
} else
err = ntfs_resident_attr_resize(ni, newsize, 0, holes);
ntfs_debug("Return status %d\n", err);