[PATCH 8/9] xfs: use iomap_valid method to detect stale cached iomaps

Dave Chinner
2022-11-15T01:31:28Z

From: Dave Chinner <dchinner@redhat.com>

Now that iomap supports a mechanism to validate cached iomaps for
buffered write operations, hook it up to the XFS buffered write ops
so that we can avoid data corruptions that result from stale cached
iomaps. See:

https://lore.kernel.org/linux-xfs/20220817093627.GZ3600936@dread.disaster.area/

or the ->iomap_valid() introduction commit for exact details of the
corruption vector.

The validity cookie we store in the iomap is based on the type of
iomap we return. It is expected that the iomap->flags we set in
xfs_bmbt_to_iomap() is not perturbed by the iomap core and are
returned to us in the iomap passed via the .iomap_valid() callback.
This ensures that the validity cookie is always checking the correct
inode fork sequence numbers to detect potential changes that affect
the extent cached by the iomap.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/libxfs/xfs_bmap.c | 6 ++-
fs/xfs/xfs_aops.c | 2 +-
fs/xfs/xfs_iomap.c | 105 +++++++++++++++++++++++++++++++--------
fs/xfs/xfs_iomap.h | 5 +-
fs/xfs/xfs_pnfs.c | 6 ++-
5 files changed, 97 insertions(+), 27 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 49d0d4ea63fc..56b9b7db38bb 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -4551,7 +4551,8 @@ xfs_bmapi_convert_delalloc(
* the extent. Just return the real extent at this offset.
*/
if (!isnullstartblock(bma.got.br_startblock)) {
- xfs_bmbt_to_iomap(ip, iomap, &bma.got, 0, flags);
+ xfs_bmbt_to_iomap(ip, iomap, &bma.got, 0, flags,
+ xfs_iomap_inode_sequence(ip, flags));
*seq = READ_ONCE(ifp->if_seq);
goto out_trans_cancel;
}
@@ -4599,7 +4600,8 @@ xfs_bmapi_convert_delalloc(
XFS_STATS_INC(mp, xs_xstrat_quick);

ASSERT(!isnullstartblock(bma.got.br_startblock));
- xfs_bmbt_to_iomap(ip, iomap, &bma.got, 0, flags);
+ xfs_bmbt_to_iomap(ip, iomap, &bma.got, 0, flags,
+ xfs_iomap_inode_sequence(ip, flags));
*seq = READ_ONCE(ifp->if_seq);

if (whichfork == XFS_COW_FORK)
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 6aadc5815068..a22d90af40c8 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -372,7 +372,7 @@ xfs_map_blocks(
isnullstartblock(imap.br_startblock))
goto allocate_blocks;

- xfs_bmbt_to_iomap(ip, &wpc->iomap, &imap, 0, 0);
+ xfs_bmbt_to_iomap(ip, &wpc->iomap, &imap, 0, 0, XFS_WPC(wpc)->data_seq);
trace_xfs_map_blocks_found(ip, offset, count, whichfork, &imap);
return 0;
allocate_blocks:
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 04da22943e7c..fa578c913323 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -48,13 +48,54 @@ xfs_alert_fsblock_zero(
return -EFSCORRUPTED;
}

+u64
+xfs_iomap_inode_sequence(
+ struct xfs_inode *ip,
+ u16 iomap_flags)
+{
+ u64 cookie = 0;
+
+ if (iomap_flags & IOMAP_F_XATTR)
+ return READ_ONCE(ip->i_af.if_seq);
+ if ((iomap_flags & IOMAP_F_SHARED) && ip->i_cowfp)
+ cookie = (u64)READ_ONCE(ip->i_cowfp->if_seq) << 32;
+ return cookie | READ_ONCE(ip->i_df.if_seq);
+}
+
+/*
+ * Check that the iomap passed to us is still valid for the given offset and
+ * length.
+ */
+static bool
+xfs_iomap_valid(
+ struct inode *inode,
+ const struct iomap *iomap)
+{
+ struct xfs_inode *ip = XFS_I(inode);
+ u64 cookie = 0;
+
+ if (iomap->flags & IOMAP_F_XATTR) {
+ cookie = READ_ONCE(ip->i_af.if_seq);
+ } else {
+ if ((iomap->flags & IOMAP_F_SHARED) && ip->i_cowfp)
+ cookie = (u64)READ_ONCE(ip->i_cowfp->if_seq) << 32;
+ cookie |= READ_ONCE(ip->i_df.if_seq);
+ }
+ return cookie == iomap->validity_cookie;
+}
+
+const struct iomap_page_ops xfs_iomap_page_ops = {
+ .iomap_valid = xfs_iomap_valid,
+};
+
int
xfs_bmbt_to_iomap(
struct xfs_inode *ip,
struct iomap *iomap,
struct xfs_bmbt_irec *imap,
unsigned int mapping_flags,
- u16 iomap_flags)
+ u16 iomap_flags,
+ u64 sequence_cookie)
{
struct xfs_mount *mp = ip->i_mount;
struct xfs_buftarg *target = xfs_inode_buftarg(ip);
@@ -91,6 +132,9 @@ xfs_bmbt_to_iomap(
if (xfs_ipincount(ip) &&
(ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
iomap->flags |= IOMAP_F_DIRTY;
+
+ iomap->validity_cookie = sequence_cookie;
+ iomap->page_ops = &xfs_iomap_page_ops;
return 0;
}

@@ -195,7 +239,8 @@ xfs_iomap_write_direct(
xfs_fileoff_t offset_fsb,
xfs_fileoff_t count_fsb,
unsigned int flags,
- struct xfs_bmbt_irec *imap)
+ struct xfs_bmbt_irec *imap,
+ u64 *seq)
{
struct xfs_mount *mp = ip->i_mount;
struct xfs_trans *tp;
@@ -285,6 +330,8 @@ xfs_iomap_write_direct(
error = xfs_alert_fsblock_zero(ip, imap);

out_unlock:
+ if (seq)
+ *seq = xfs_iomap_inode_sequence(ip, 0);
xfs_iunlock(ip, XFS_ILOCK_EXCL);
return error;

@@ -743,6 +790,7 @@ xfs_direct_write_iomap_begin(
bool shared = false;
u16 iomap_flags = 0;
unsigned int lockmode = XFS_ILOCK_SHARED;
+ u64 seq;

ASSERT(flags & (IOMAP_WRITE | IOMAP_ZERO));

@@ -811,9 +859,10 @@ xfs_direct_write_iomap_begin(
goto out_unlock;
}

+ seq = xfs_iomap_inode_sequence(ip, iomap_flags);
xfs_iunlock(ip, lockmode);
trace_xfs_iomap_found(ip, offset, length, XFS_DATA_FORK, &imap);
- return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, iomap_flags);
+ return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, iomap_flags, seq);

allocate_blocks:
error = -EAGAIN;
@@ -839,24 +888,26 @@ xfs_direct_write_iomap_begin(
xfs_iunlock(ip, lockmode);

error = xfs_iomap_write_direct(ip, offset_fsb, end_fsb - offset_fsb,
- flags, &imap);
+ flags, &imap, &seq);
if (error)
return error;

trace_xfs_iomap_alloc(ip, offset, length, XFS_DATA_FORK, &imap);
return xfs_bmbt_to_iomap(ip, iomap, &imap, flags,
- iomap_flags | IOMAP_F_NEW);
+ iomap_flags | IOMAP_F_NEW, seq);

out_found_cow:
- xfs_iunlock(ip, lockmode);
length = XFS_FSB_TO_B(mp, cmap.br_startoff + cmap.br_blockcount);
trace_xfs_iomap_found(ip, offset, length - offset, XFS_COW_FORK, &cmap);
if (imap.br_startblock != HOLESTARTBLOCK) {
- error = xfs_bmbt_to_iomap(ip, srcmap, &imap, flags, 0);
+ seq = xfs_iomap_inode_sequence(ip, 0);
+ error = xfs_bmbt_to_iomap(ip, srcmap, &imap, flags, 0, seq);
if (error)
- return error;
+ goto out_unlock;
}
- return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags, IOMAP_F_SHARED);
+ seq = xfs_iomap_inode_sequence(ip, IOMAP_F_SHARED);
+ xfs_iunlock(ip, lockmode);
+ return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags, IOMAP_F_SHARED, seq);

out_unlock:
if (lockmode)
@@ -915,6 +966,7 @@ xfs_buffered_write_iomap_begin(
int allocfork = XFS_DATA_FORK;
int error = 0;
unsigned int lockmode = XFS_ILOCK_EXCL;
+ u64 seq;

if (xfs_is_shutdown(mp))
return -EIO;
@@ -1094,26 +1146,31 @@ xfs_buffered_write_iomap_begin(
* Flag newly allocated delalloc blocks with IOMAP_F_NEW so we punch
* them out if the write happens to fail.
*/
+ seq = xfs_iomap_inode_sequence(ip, IOMAP_F_NEW);
xfs_iunlock(ip, XFS_ILOCK_EXCL);
trace_xfs_iomap_alloc(ip, offset, count, allocfork, &imap);
- return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, IOMAP_F_NEW);
+ return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, IOMAP_F_NEW, seq);

found_imap:
+ seq = xfs_iomap_inode_sequence(ip, 0);
xfs_iunlock(ip, XFS_ILOCK_EXCL);
- return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, 0);
+ return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, 0, seq);

found_cow:
- xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ seq = xfs_iomap_inode_sequence(ip, 0);
if (imap.br_startoff <= offset_fsb) {
- error = xfs_bmbt_to_iomap(ip, srcmap, &imap, flags, 0);
+ error = xfs_bmbt_to_iomap(ip, srcmap, &imap, flags, 0, seq);
if (error)
- return error;
+ goto out_unlock;
+ seq = xfs_iomap_inode_sequence(ip, IOMAP_F_SHARED);
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags,
- IOMAP_F_SHARED);
+ IOMAP_F_SHARED, seq);
}

xfs_trim_extent(&cmap, offset_fsb, imap.br_startoff - offset_fsb);
- return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags, 0);
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags, 0, seq);

out_unlock:
xfs_iunlock(ip, XFS_ILOCK_EXCL);
@@ -1346,6 +1403,7 @@ xfs_read_iomap_begin(
int nimaps = 1, error = 0;
bool shared = false;
unsigned int lockmode = XFS_ILOCK_SHARED;
+ u64 seq;

ASSERT(!(flags & (IOMAP_WRITE | IOMAP_ZERO)));

@@ -1359,13 +1417,14 @@ xfs_read_iomap_begin(
&nimaps, 0);
if (!error && (flags & IOMAP_REPORT))
error = xfs_reflink_trim_around_shared(ip, &imap, &shared);
+ seq = xfs_iomap_inode_sequence(ip, shared ? IOMAP_F_SHARED : 0);
xfs_iunlock(ip, lockmode);

if (error)
return error;
trace_xfs_iomap_found(ip, offset, length, XFS_DATA_FORK, &imap);
return xfs_bmbt_to_iomap(ip, iomap, &imap, flags,
- shared ? IOMAP_F_SHARED : 0);
+ shared ? IOMAP_F_SHARED : 0, seq);
}

const struct iomap_ops xfs_read_iomap_ops = {
@@ -1390,6 +1449,7 @@ xfs_seek_iomap_begin(
struct xfs_bmbt_irec imap, cmap;
int error = 0;
unsigned lockmode;
+ u64 seq;

if (xfs_is_shutdown(mp))
return -EIO;
@@ -1424,8 +1484,9 @@ xfs_seek_iomap_begin(
if (data_fsb < cow_fsb + cmap.br_blockcount)
end_fsb = min(end_fsb, data_fsb);
xfs_trim_extent(&cmap, offset_fsb, end_fsb);
+ seq = xfs_iomap_inode_sequence(ip, IOMAP_F_SHARED);
error = xfs_bmbt_to_iomap(ip, iomap, &cmap, flags,
- IOMAP_F_SHARED);
+ IOMAP_F_SHARED, seq);
/*
* This is a COW extent, so we must probe the page cache
* because there could be dirty page cache being backed
@@ -1446,8 +1507,9 @@ xfs_seek_iomap_begin(
imap.br_startblock = HOLESTARTBLOCK;
imap.br_state = XFS_EXT_NORM;
done:
+ seq = xfs_iomap_inode_sequence(ip, 0);
xfs_trim_extent(&imap, offset_fsb, end_fsb);
- error = xfs_bmbt_to_iomap(ip, iomap, &imap, flags, 0);
+ error = xfs_bmbt_to_iomap(ip, iomap, &imap, flags, 0, seq);
out_unlock:
xfs_iunlock(ip, lockmode);
return error;
@@ -1473,6 +1535,7 @@ xfs_xattr_iomap_begin(
struct xfs_bmbt_irec imap;
int nimaps = 1, error = 0;
unsigned lockmode;
+ int seq;

if (xfs_is_shutdown(mp))
return -EIO;
@@ -1489,12 +1552,14 @@ xfs_xattr_iomap_begin(
error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
&nimaps, XFS_BMAPI_ATTRFORK);
out_unlock:
+
+ seq = xfs_iomap_inode_sequence(ip, IOMAP_F_XATTR);
xfs_iunlock(ip, lockmode);

if (error)
return error;
ASSERT(nimaps);
- return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, 0);
+ return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, IOMAP_F_XATTR, seq);
}

const struct iomap_ops xfs_xattr_iomap_ops = {
diff --git a/fs/xfs/xfs_iomap.h b/fs/xfs/xfs_iomap.h
index 0f62ab633040..4da13440bae9 100644
--- a/fs/xfs/xfs_iomap.h
+++ b/fs/xfs/xfs_iomap.h
@@ -13,14 +13,15 @@ struct xfs_bmbt_irec;

int xfs_iomap_write_direct(struct xfs_inode *ip, xfs_fileoff_t offset_fsb,
xfs_fileoff_t count_fsb, unsigned int flags,
- struct xfs_bmbt_irec *imap);
+ struct xfs_bmbt_irec *imap, u64 *sequence);
int xfs_iomap_write_unwritten(struct xfs_inode *, xfs_off_t, xfs_off_t, bool);
xfs_fileoff_t xfs_iomap_eof_align_last_fsb(struct xfs_inode *ip,
xfs_fileoff_t end_fsb);

+u64 xfs_iomap_inode_sequence(struct xfs_inode *ip, u16 iomap_flags);
int xfs_bmbt_to_iomap(struct xfs_inode *ip, struct iomap *iomap,
struct xfs_bmbt_irec *imap, unsigned int mapping_flags,
- u16 iomap_flags);
+ u16 iomap_flags, u64 sequence_cookie);

int xfs_zero_range(struct xfs_inode *ip, loff_t pos, loff_t len,
bool *did_zero);
diff --git a/fs/xfs/xfs_pnfs.c b/fs/xfs/xfs_pnfs.c
index 37a24f0f7cd4..38d23f0e703a 100644
--- a/fs/xfs/xfs_pnfs.c
+++ b/fs/xfs/xfs_pnfs.c
@@ -125,6 +125,7 @@ xfs_fs_map_blocks(
int nimaps = 1;
uint lock_flags;
int error = 0;
+ u64 seq;

if (xfs_is_shutdown(mp))
return -EIO;
@@ -176,6 +177,7 @@ xfs_fs_map_blocks(
lock_flags = xfs_ilock_data_map_shared(ip);
error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb,
&imap, &nimaps, bmapi_flags);
+ seq = xfs_iomap_inode_sequence(ip, 0);

ASSERT(!nimaps || imap.br_startblock != DELAYSTARTBLOCK);

@@ -189,7 +191,7 @@ xfs_fs_map_blocks(
xfs_iunlock(ip, lock_flags);

error = xfs_iomap_write_direct(ip, offset_fsb,
- end_fsb - offset_fsb, 0, &imap);
+ end_fsb - offset_fsb, 0, &imap, &seq);
if (error)
goto out_unlock;

@@ -209,7 +211,7 @@ xfs_fs_map_blocks(
}
xfs_iunlock(ip, XFS_IOLOCK_EXCL);

- error = xfs_bmbt_to_iomap(ip, iomap, &imap, 0, 0);
+ error = xfs_bmbt_to_iomap(ip, iomap, &imap, 0, 0, seq);
*device_generation = mp->m_generation;
return error;
out_unlock:
--
2.37.2