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xfs: xfs_seek_hole() refinement with hole searching from page cache for unwritten extents 

xfs_seek_hole() refinement with hole searching from page cache for unwritten extent.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
This commit is contained in:
Jeff Liu 2012-08-21 17:12:18 +08:00 committed by Ben Myers
parent 52f1acc8b5
commit b686d1f79a
1 changed files with 67 additions and 11 deletions
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78
fs/xfs/xfs_file.c
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@ -1289,9 +1289,9 @@ xfs_seek_hole(
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
loff_t uninitialized_var(offset);
loff_t holeoff;
xfs_fsize_t isize;
xfs_fileoff_t fsbno;
xfs_filblks_t end;
uint lock;
int error;
@ -1307,21 +1307,77 @@ xfs_seek_hole(
}
fsbno = XFS_B_TO_FSBT(mp, start);
error = xfs_bmap_first_unused(NULL, ip, 1, &fsbno, XFS_DATA_FORK);
end = XFS_B_TO_FSB(mp, isize);
for (;;) {
struct xfs_bmbt_irec map[2];
int nmap = 2;
unsigned int i;
error = xfs_bmapi_read(ip, fsbno, end - fsbno, map, &nmap,
XFS_BMAPI_ENTIRE);
if (error)
goto out_unlock;
holeoff = XFS_FSB_TO_B(mp, fsbno);
if (holeoff <= start)
offset = start;
else {
/*
* xfs_bmap_first_unused() could return a value bigger than
* isize if there are no more holes past the supplied offset.
*/
offset = min_t(loff_t, holeoff, isize);
/* No extents at given offset, must be beyond EOF */
if (nmap == 0) {
error = ENXIO;
goto out_unlock;
}
for (i = 0; i < nmap; i++) {
offset = max_t(loff_t, start,
XFS_FSB_TO_B(mp, map[i].br_startoff));
/* Landed in a hole */
if (map[i].br_startblock == HOLESTARTBLOCK)
goto out;
/*
* Landed in an unwritten extent, try to search hole
* from page cache.
*/
if (map[i].br_state == XFS_EXT_UNWRITTEN) {
if (xfs_find_get_desired_pgoff(inode, &map[i],
HOLE_OFF, &offset))
goto out;
}
}
/*
* map[0] contains data or its unwritten but contains
* data in page cache, probably means that we are
* reading after EOF. We should fix offset to point
* to the end of the file(i.e., there is an implicit
* hole at the end of any file).
*/
if (nmap == 1) {
offset = isize;
break;
}
ASSERT(i > 1);
/*
* Both mappings contains data, proceed to the next round of
* search if the current reading offset not beyond or hit EOF.
*/
fsbno = map[i - 1].br_startoff + map[i - 1].br_blockcount;
start = XFS_FSB_TO_B(mp, fsbno);
if (start >= isize) {
offset = isize;
break;
}
}
out:
/*
* At this point, we must have found a hole. However, the returned
* offset may be bigger than the file size as it may be aligned to
* page boundary for unwritten extents, we need to deal with this
* situation in particular.
*/
offset = min_t(loff_t, offset, isize);
if (offset != file->f_pos)
file->f_pos = offset;