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xfs: make COW fork unwritten extent conversions more robust

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If we have racing buffered and direct I/O COW fork extents under
writeback can have been moved to the data fork by the time we call
xfs_reflink_convert_cow from xfs_submit_ioend.  This would be mostly
harmless as the block numbers don't change by this move, except for
the fact that xfs_bmapi_write will crash or trigger asserts when
not finding existing extents, even despite trying to paper over this
with the XFS_BMAPI_CONVERT_ONLY flag.

Instead of special casing non-transaction conversions in the already
way too complicated xfs_bmapi_write just add a new helper for the much
simpler non-transactional COW fork case, which simplify ignores not
found extents.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Christoph Hellwig 2019-02-18 09:38:48 -08:00 committed by Darrick J. Wong
parent db46e604ad
commit 26b91c728b
3 changed files with 45 additions and 33 deletions
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9
fs/xfs/libxfs/xfs_bmap.c
View File

@ -2031,7 +2031,7 @@ done:
/*
* Convert an unwritten allocation to a real allocation or vice versa.
*/
STATIC int /* error */
int /* error */
xfs_bmap_add_extent_unwritten_real(
struct xfs_trans *tp,
xfs_inode_t *ip, /* incore inode pointer */
@ -4276,9 +4276,7 @@ xfs_bmapi_write(
ASSERT(*nmap >= 1);
ASSERT(*nmap <= XFS_BMAP_MAX_NMAP);
ASSERT(tp != NULL ||
(flags & (XFS_BMAPI_CONVERT | XFS_BMAPI_COWFORK)) ==
(XFS_BMAPI_CONVERT | XFS_BMAPI_COWFORK));
ASSERT(tp != NULL);
ASSERT(len > 0);
ASSERT(XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_LOCAL);
ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
@ -4352,8 +4350,7 @@ xfs_bmapi_write(
* First, deal with the hole before the allocated space
* that we found, if any.
*/
if ((need_alloc || wasdelay) &&
!(flags & XFS_BMAPI_CONVERT_ONLY)) {
if (need_alloc || wasdelay) {
bma.eof = eof;
bma.conv = !!(flags & XFS_BMAPI_CONVERT);
bma.wasdel = wasdelay;

8
fs/xfs/libxfs/xfs_bmap.h
View File

@ -95,9 +95,6 @@ struct xfs_extent_free_item
/* Map something in the CoW fork. */
#define XFS_BMAPI_COWFORK 0x200
/* Only convert unwritten extents, don't allocate new blocks */
#define XFS_BMAPI_CONVERT_ONLY 0x800
/* Skip online discard of freed extents */
#define XFS_BMAPI_NODISCARD 0x1000
@ -114,7 +111,6 @@ struct xfs_extent_free_item
{ XFS_BMAPI_ZERO, "ZERO" }, \
{ XFS_BMAPI_REMAP, "REMAP" }, \
{ XFS_BMAPI_COWFORK, "COWFORK" }, \
{ XFS_BMAPI_CONVERT_ONLY, "CONVERT_ONLY" }, \
{ XFS_BMAPI_NODISCARD, "NODISCARD" }, \
{ XFS_BMAPI_NORMAP, "NORMAP" }
@ -226,6 +222,10 @@ int xfs_bmapi_reserve_delalloc(struct xfs_inode *ip, int whichfork,
int xfs_bmapi_convert_delalloc(struct xfs_inode *ip, int whichfork,
xfs_fileoff_t offset_fsb, struct xfs_bmbt_irec *imap,
unsigned int *seq);
int xfs_bmap_add_extent_unwritten_real(struct xfs_trans *tp,
struct xfs_inode *ip, int whichfork,
struct xfs_iext_cursor *icur, struct xfs_btree_cur **curp,
struct xfs_bmbt_irec *new, int *logflagsp);
static inline void
xfs_bmap_add_free(

61
fs/xfs/xfs_reflink.c
View File

@ -234,26 +234,42 @@ xfs_reflink_trim_around_shared(
}
}
/* Convert part of an unwritten CoW extent to a real one. */
STATIC int
xfs_reflink_convert_cow_extent(
struct xfs_inode *ip,
struct xfs_bmbt_irec *imap,
xfs_fileoff_t offset_fsb,
xfs_filblks_t count_fsb)
static int
xfs_reflink_convert_cow_locked(
struct xfs_inode *ip,
xfs_fileoff_t offset_fsb,
xfs_filblks_t count_fsb)
{
int nimaps = 1;
struct xfs_iext_cursor icur;
struct xfs_bmbt_irec got;
struct xfs_btree_cur *dummy_cur = NULL;
int dummy_logflags;
int error;
if (imap->br_state == XFS_EXT_NORM)
if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &got))
return 0;
xfs_trim_extent(imap, offset_fsb, count_fsb);
trace_xfs_reflink_convert_cow(ip, imap);
if (imap->br_blockcount == 0)
return 0;
return xfs_bmapi_write(NULL, ip, imap->br_startoff, imap->br_blockcount,
XFS_BMAPI_COWFORK | XFS_BMAPI_CONVERT, 0, imap,
&nimaps);
do {
if (got.br_startoff >= offset_fsb + count_fsb)
break;
if (got.br_state == XFS_EXT_NORM)
continue;
if (WARN_ON_ONCE(isnullstartblock(got.br_startblock)))
return -EIO;
xfs_trim_extent(&got, offset_fsb, count_fsb);
if (!got.br_blockcount)
continue;
got.br_state = XFS_EXT_NORM;
error = xfs_bmap_add_extent_unwritten_real(NULL, ip,
XFS_COW_FORK, &icur, &dummy_cur, &got,
&dummy_logflags);
if (error)
return error;
} while (xfs_iext_next_extent(ip->i_cowfp, &icur, &got));
return error;
}
/* Convert all of the unwritten CoW extents in a file's range to real ones. */
@ -267,15 +283,12 @@ xfs_reflink_convert_cow(
xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset);
xfs_fileoff_t end_fsb = XFS_B_TO_FSB(mp, offset + count);
xfs_filblks_t count_fsb = end_fsb - offset_fsb;
struct xfs_bmbt_irec imap;
int nimaps = 1, error = 0;
int error;
ASSERT(count != 0);
xfs_ilock(ip, XFS_ILOCK_EXCL);
error = xfs_bmapi_write(NULL, ip, offset_fsb, count_fsb,
XFS_BMAPI_COWFORK | XFS_BMAPI_CONVERT |
XFS_BMAPI_CONVERT_ONLY, 0, &imap, &nimaps);
error = xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb);
xfs_iunlock(ip, XFS_ILOCK_EXCL);
return error;
}
@ -405,14 +418,16 @@ xfs_reflink_allocate_cow(
if (nimaps == 0)
return -ENOSPC;
convert:
xfs_trim_extent(imap, offset_fsb, count_fsb);
/*
* COW fork extents are supposed to remain unwritten until we're ready
* to initiate a disk write. For direct I/O we are going to write the
* data and need the conversion, but for buffered writes we're done.
*/
if (!(iomap_flags & IOMAP_DIRECT))
if (!(iomap_flags & IOMAP_DIRECT) || imap->br_state == XFS_EXT_NORM)
return 0;
return xfs_reflink_convert_cow_extent(ip, imap, offset_fsb, count_fsb);
trace_xfs_reflink_convert_cow(ip, imap);
return xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb);
out_unreserve:
xfs_trans_unreserve_quota_nblks(tp, ip, (long)resblks, 0,