[PATCH 06/10] xfs: simplify xfs_map_blocks

Christoph Hellwig
2010-11-22T13:07:27Z

[-- Attachment #1: xfs-simplify-map_blocks --]
[-- Type: text/plain, Size: 3708 bytes --]

No need to lock the extent map exclusive when performing an overwrite,
we know the extent map must already have been loaded by get_blocks.
Apply the non-blocking inode semantics to all mapping types instead of
just delayed allocations. Remove the handling of not yet allocated
blocks for the IO_UNWRITTEN case - if an extent is marked as delayed
allocated in the buffer it must already have an extent on disk.

Add asserts to verify all the assumptions above in debug builds.

Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: xfs/fs/xfs/linux-2.6/xfs_aops.c
===================================================================
--- xfs.orig/fs/xfs/linux-2.6/xfs_aops.c 2010-10-31 15:10:59.000000000 -0400
+++ xfs/fs/xfs/linux-2.6/xfs_aops.c 2010-10-31 15:13:27.777719469 -0400
@@ -313,81 +313,54 @@ xfs_map_blocks(
struct xfs_mount *mp = ip->i_mount;
xfs_fileoff_t offset_fsb, end_fsb;
int error = 0;
- int lockmode = 0;
int bmapi_flags = XFS_BMAPI_ENTIRE;
int nimaps = 1;

if (XFS_FORCED_SHUTDOWN(mp))
return -XFS_ERROR(EIO);

- switch (type) {
- case IO_OVERWRITE:
- lockmode = xfs_ilock_map_shared(ip);
- break;
- case IO_UNWRITTEN:
- lockmode = XFS_ILOCK_EXCL;
+ if (type == IO_UNWRITTEN)
bmapi_flags |= XFS_BMAPI_IGSTATE;
- xfs_ilock(ip, lockmode);
- break;
- case IO_DELALLOC:
- lockmode = XFS_ILOCK_SHARED;
-
- if (!xfs_ilock_nowait(ip, lockmode)) {
- if (nonblocking)
- return -XFS_ERROR(EAGAIN);
- xfs_ilock(ip, lockmode);
- }
- break;
+
+ if (!xfs_ilock_nowait(ip, XFS_ILOCK_SHARED)) {
+ if (nonblocking)
+ return -XFS_ERROR(EAGAIN);
+ xfs_ilock(ip, XFS_ILOCK_SHARED);
}

+ ASSERT(ip->i_d.di_format != XFS_DINODE_FMT_BTREE ||
+ (ip->i_df.if_flags & XFS_IFEXTENTS));
ASSERT(offset <= mp->m_maxioffset);
+
if (offset + count > mp->m_maxioffset)
count = mp->m_maxioffset - offset;
end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + count);
offset_fsb = XFS_B_TO_FSBT(mp, offset);
-
error = xfs_bmapi(NULL, ip, offset_fsb, end_fsb - offset_fsb,
bmapi_flags, NULL, 0, imap, &nimaps, NULL);
- if (error)
- goto out;
-
- switch (type) {
- case IO_UNWRITTEN:
- /* If we found an extent, return it */
- if (nimaps &&
- (imap->br_startblock != HOLESTARTBLOCK) &&
- (imap->br_startblock != DELAYSTARTBLOCK)) {
- trace_xfs_map_blocks_found(ip, offset, count, type, imap);
- break;
- }
+ xfs_iunlock(ip, XFS_ILOCK_SHARED);

- error = xfs_iomap_write_delay(ip, offset, count, imap);
- if (!error)
- trace_xfs_map_blocks_alloc(ip, offset, count, type, imap);
- break;
- case IO_DELALLOC:
- /* If we found an extent, return it */
- xfs_iunlock(ip, lockmode);
- lockmode = 0;
-
- if (nimaps && !isnullstartblock(imap->br_startblock)) {
- trace_xfs_map_blocks_found(ip, offset, count, type, imap);
- break;
- }
+ if (error)
+ return -XFS_ERROR(error);

+ if (type == IO_DELALLOC &&
+ (!nimaps || isnullstartblock(imap->br_startblock))) {
error = xfs_iomap_write_allocate(ip, offset, count, imap);
if (!error)
trace_xfs_map_blocks_alloc(ip, offset, count, type, imap);
- break;
- default:
- if (nimaps)
- trace_xfs_map_blocks_found(ip, offset, count, type, imap);
+ return -XFS_ERROR(error);
}

-out:
- if (lockmode)
- xfs_iunlock(ip, lockmode);
- return -XFS_ERROR(error);
+#ifdef DEBUG
+ if (type == IO_UNWRITTEN) {
+ ASSERT(nimaps);
+ ASSERT(imap->br_startblock != HOLESTARTBLOCK);
+ ASSERT(imap->br_startblock != DELAYSTARTBLOCK);
+ }
+#endif
+ if (nimaps)
+ trace_xfs_map_blocks_found(ip, offset, count, type, imap);
+ return 0;
}

STATIC int