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ntfs: do not turn an unmappable runlist fragment into delalloc on write

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ntfs_write_simple_iomap_begin_non_resident() has the same unchecked
retry.  LCN_RL_NOT_MAPPED passes its "lcn <= LCN_HOLE" test, so a
buffered write into a range whose extent record cannot be read is
merged into the runlist as LCN_DELALLOC over clusters that are already
allocated on disk, and write() succeeds.  If the record stays
unreadable, writeback fails too and the data never reaches the disk;
the error only shows up at a later fsync() or a synchronous write.

On the volume from the previous patch, after a read of the file, an
8 KiB pwrite() at vcn 1000 returns 8192, fsync() returns -EIO, and
after remount the range is unchanged.

Fail the lookup here too, with -ENOMEM or -EIO.  That pwrite() now
fails with -EIO.  Writes whose range can be mapped are unaffected.

Fixes: b041ca5625 ("ntfs: update iomap and address space operations")
Cc: stable@vger.kernel.org
Signed-off-by: Matthias Goergens <matthias.goergens@gmail.com>
Reviewed-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
This commit is contained in:
Matthias Goergens 2026-09-30 11:48:31 +08:00 committed by Namjae Jeon
parent 2b451a6565
commit 26e51efbcb
1 changed files with 14 additions and 2 deletions
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16
fs/ntfs/iomap.c
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@ -394,7 +394,7 @@ static int ntfs_write_simple_iomap_begin_non_resident(struct inode *inode, loff_
loff_t vcn_ofs, rl_length;
struct runlist_element *rl, *rlc;
bool is_retry = false;
int err = 0;
int err = 0, map_err = 0;
s64 vcn, lcn;
s64 max_clu_count =
ntfs_bytes_to_cluster(vol, round_up(length, vol->cluster_size));
@ -429,12 +429,24 @@ static int ntfs_write_simple_iomap_begin_non_resident(struct inode *inode, loff_
if (lcn <= LCN_RL_NOT_MAPPED && is_retry == false) {
is_retry = true;
if (!ntfs_map_runlist_nolock(ni, vcn, NULL)) {
map_err = ntfs_map_runlist_nolock(ni, vcn, NULL);
if (!map_err) {
rl = ni->runlist.rl;
goto remap_rl;
}
}
/*
* As in ntfs_attr_vcn_to_rl(): a runlist fragment that could not be
* mapped is not a hole. Treating it as one would put a delalloc
* extent over clusters that are allocated on disk but unknown to us.
*/
if (lcn == LCN_RL_NOT_MAPPED) {
up_write(&ni->runlist.lock);
mutex_unlock(&ni->mrec_lock);
return map_err == -ENOMEM ? -ENOMEM : -EIO;
}
max_clu_count = min(max_clu_count, rl->length - (vcn - rl->vcn));
if (max_clu_count == 0) {
ntfs_error(inode->i_sb,