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xfs: report shared extent mappings to userspace correctly

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Report shared extents through the iomap interface so that FIEMAP flags
shared blocks accurately.  Have xfs_vm_bmap return zero for reflinked
files because the bmap-based swap code requires static block mappings,
which is incompatible with copy on write.

NOTE: Existing userspace bmap users such as lilo will have the same
problem with reflink files.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Darrick J. Wong 2016-10-03 09:11:36 -07:00
parent 43caeb187d
commit db1327b16c
2 changed files with 22 additions and 1 deletions
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11
fs/xfs/xfs_aops.c
View File

@ -1508,6 +1508,17 @@ xfs_vm_bmap(
trace_xfs_vm_bmap(XFS_I(inode));
xfs_ilock(ip, XFS_IOLOCK_SHARED);
/*
* The swap code (ab-)uses ->bmap to get a block mapping and then
* bypasseѕ the file system for actual I/O. We really can't allow
* that on reflinks inodes, so we have to skip out here. And yes,
* 0 is the magic code for a bmap error..
*/
if (xfs_is_reflink_inode(ip)) {
xfs_iunlock(ip, XFS_IOLOCK_SHARED);
return 0;
}
filemap_write_and_wait(mapping);
xfs_iunlock(ip, XFS_IOLOCK_SHARED);
return generic_block_bmap(mapping, block, xfs_get_blocks);

12
fs/xfs/xfs_iomap.c
View File

@ -961,6 +961,7 @@ xfs_file_iomap_begin(
struct xfs_mount *mp = ip->i_mount;
struct xfs_bmbt_irec imap;
xfs_fileoff_t offset_fsb, end_fsb;
bool shared, trimmed;
int nimaps = 1, error = 0;
unsigned lockmode;
@ -989,7 +990,14 @@ xfs_file_iomap_begin(
end_fsb = XFS_B_TO_FSB(mp, offset + length);
error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
&nimaps, XFS_BMAPI_ENTIRE);
&nimaps, 0);
if (error) {
xfs_iunlock(ip, lockmode);
return error;
}
/* Trim the mapping to the nearest shared extent boundary. */
error = xfs_reflink_trim_around_shared(ip, &imap, &shared, &trimmed);
if (error) {
xfs_iunlock(ip, lockmode);
return error;
@ -1028,6 +1036,8 @@ xfs_file_iomap_begin(
}
xfs_bmbt_to_iomap(ip, iomap, &imap);
if (shared)
iomap->flags |= IOMAP_F_SHARED;
return 0;
}