[PATCH v2 1/2] fs/ntfs3: load ATTR_BITMAP run extents from $MFT extension records

[Senjin <senjin@hatchling.org>]

v2: fix malformed hunk header in patch (no code change)

When $MFT's ATTR_BITMAP attribute is heavily fragmented, its run list
can span multiple MFT extension records (attribute list entries with
vcn > 0). The non-primary segment handler in ntfs_read_mft() only
processed ATTR_DATA extension segments for MFT_REC_MFT, silently
skipping any ATTR_BITMAP segments. This left sbi->mft.bitmap.run
incomplete, causing wnd_init() to fail with -ENOENT when wnd_rescan()
tried to look up a VCN not covered by the truncated run list.

Observed on a 16 TB NTFS volume (0xFFFFFEFF total clusters) whose MFT
bitmap run list was split across 97 extents in extension records.
wnd_rescan() successfully looked up VCNs 0-122 from the runs loaded
from the base record, then failed at VCN 123 (the last cluster of the
bitmap) whose run was only present in an extension record.

Fix by extending the MFT_REC_MFT special case to also handle
ATTR_BITMAP extension segments, storing their runs into
sbi->mft.bitmap.run the same way the primary segment does.

Signed-off-by: Senjin <senjin@hatchling.org>
---
 fs/ntfs3/inode.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/ntfs3/inode.c b/fs/ntfs3/inode.c
index XXXXXXX..XXXXXXX 100644
--- a/fs/ntfs3/inode.c
+++ b/fs/ntfs3/inode.c
@@ -127,10 +127,16 @@ static struct inode *ntfs_read_mft(struct inode *inode,

 	if (le && le->vcn) {
 		/* This is non primary attribute segment. Ignore if not MFT. */
-		if (ino != MFT_REC_MFT || attr->type != ATTR_DATA)
+		if (ino != MFT_REC_MFT)
 			goto next_attr;

-		run = &ni->file.run;
+		if (attr->type == ATTR_DATA)
+			run = &ni->file.run;
+		else if (attr->type == ATTR_BITMAP)
+			run = &sbi->mft.bitmap.run;
+		else
+			goto next_attr;
+
 		asize = le32_to_cpu(attr->size);
 		goto attr_unpack_run;
 	}
--
2.x