xfs: rewrite and optimize the delalloc write path

Source kernel commit: 51446f5ba44874db4d2a93a6eb61b133e5ec1b3e

Currently xfs_iomap_write_delay does up to lookups in the inode
extent tree, which is rather costly especially with the new iomap
based write path and small write sizes.

But it turns out that the low-level xfs_bmap_search_extents gives us
all the information we need in the regular delalloc buffered write
path:

- it will return us an extent covering the block we are looking up
if it exists.  In that case we can simply return that extent to
the caller and are done
- it will tell us if we are beyoned the last current allocated
block with an eof return parameter.  In that case we can create a
delalloc reservation and use the also returned information about
the last extent in the file as the hint to size our delalloc
reservation.
- it can tell us that we are writing into a hole, but that there is
an extent beyoned this hole.  In this case we can create a
delalloc reservation that covers the requested size (possible
capped to the next existing allocation).

All that can be done in one single routine instead of bouncing up
and down a few layers.  This reduced the CPU overhead of the block
mapping routines and also simplified the code a lot.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/libxfs/xfs_bmap.c b/libxfs/xfs_bmap.c
index a50a8af0c3bc35b118832eadb167560ddc4678b0..f137a877b0717042c15bd153775300e4fa1ea641 100644 (file)
--- a/libxfs/xfs_bmap.c
+++ b/libxfs/xfs_bmap.c
@@ -4068,7 +4068,7 @@ xfs_bmapi_read(
        return 0;
 }
 
-STATIC int
+int
 xfs_bmapi_reserve_delalloc(
        struct xfs_inode        *ip,
        xfs_fileoff_t           aoff,
@@ -4164,91 +4164,6 @@ out_unreserve_quota:
        return error;
 }
 
-/*
- * Map file blocks to filesystem blocks, adding delayed allocations as needed.
- */
-int
-xfs_bmapi_delay(
-       struct xfs_inode        *ip,    /* incore inode */
-       xfs_fileoff_t           bno,    /* starting file offs. mapped */
-       xfs_filblks_t           len,    /* length to map in file */
-       struct xfs_bmbt_irec    *mval,  /* output: map values */
-       int                     *nmap,  /* i/o: mval size/count */
-       int                     flags)  /* XFS_BMAPI_... */
-{
-       struct xfs_mount        *mp = ip->i_mount;
-       struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
-       struct xfs_bmbt_irec    got;    /* current file extent record */
-       struct xfs_bmbt_irec    prev;   /* previous file extent record */
-       xfs_fileoff_t           obno;   /* old block number (offset) */
-       xfs_fileoff_t           end;    /* end of mapped file region */
-       xfs_extnum_t            lastx;  /* last useful extent number */
-       int                     eof;    /* we've hit the end of extents */
-       int                     n = 0;  /* current extent index */
-       int                     error = 0;
-
-       ASSERT(*nmap >= 1);
-       ASSERT(*nmap <= XFS_BMAP_MAX_NMAP);
-       ASSERT(!(flags & ~XFS_BMAPI_ENTIRE));
-       ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
-
-       if (unlikely(XFS_TEST_ERROR(
-           (XFS_IFORK_FORMAT(ip, XFS_DATA_FORK) != XFS_DINODE_FMT_EXTENTS &&
-            XFS_IFORK_FORMAT(ip, XFS_DATA_FORK) != XFS_DINODE_FMT_BTREE),
-            mp, XFS_ERRTAG_BMAPIFORMAT, XFS_RANDOM_BMAPIFORMAT))) {
-               XFS_ERROR_REPORT("xfs_bmapi_delay", XFS_ERRLEVEL_LOW, mp);
-               return -EFSCORRUPTED;
-       }
-
-       if (XFS_FORCED_SHUTDOWN(mp))
-               return -EIO;
-
-       XFS_STATS_INC(mp, xs_blk_mapw);
-
-       if (!(ifp->if_flags & XFS_IFEXTENTS)) {
-               error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
-               if (error)
-                       return error;
-       }
-
-       xfs_bmap_search_extents(ip, bno, XFS_DATA_FORK, &eof, &lastx, &got, &prev);
-       end = bno + len;
-       obno = bno;
-
-       while (bno < end && n < *nmap) {
-               if (eof || got.br_startoff > bno) {
-                       error = xfs_bmapi_reserve_delalloc(ip, bno, len, &got,
-                                                          &prev, &lastx, eof);
-                       if (error) {
-                               if (n == 0) {
-                                       *nmap = 0;
-                                       return error;
-                               }
-                               break;
-                       }
-               }
-
-               /* set up the extent map to return. */
-               xfs_bmapi_trim_map(mval, &got, &bno, len, obno, end, n, flags);
-               xfs_bmapi_update_map(&mval, &bno, &len, obno, end, &n, flags);
-
-               /* If we're done, stop now. */
-               if (bno >= end || n >= *nmap)
-                       break;
-
-               /* Else go on to the next record. */
-               prev = got;
-               if (++lastx < ifp->if_bytes / sizeof(xfs_bmbt_rec_t))
-                       xfs_bmbt_get_all(xfs_iext_get_ext(ifp, lastx), &got);
-               else
-                       eof = 1;
-       }
-
-       *nmap = n;
-       return 0;
-}
-
-
 static int
 xfs_bmapi_allocate(
        struct xfs_bmalloca     *bma)

diff --git a/libxfs/xfs_bmap.h b/libxfs/xfs_bmap.h
index 9220b1d7d43c7013a66d2c8658cc66176527124b..49050fd074dbb97b53351067e5486c8920e7fa60 100644 (file)
--- a/libxfs/xfs_bmap.h
+++ b/libxfs/xfs_bmap.h
@@ -181,9 +181,6 @@ int xfs_bmap_read_extents(struct xfs_trans *tp, struct xfs_inode *ip,
 int    xfs_bmapi_read(struct xfs_inode *ip, xfs_fileoff_t bno,
                xfs_filblks_t len, struct xfs_bmbt_irec *mval,
                int *nmap, int flags);
-int    xfs_bmapi_delay(struct xfs_inode *ip, xfs_fileoff_t bno,
-               xfs_filblks_t len, struct xfs_bmbt_irec *mval,
-               int *nmap, int flags);
 int    xfs_bmapi_write(struct xfs_trans *tp, struct xfs_inode *ip,
                xfs_fileoff_t bno, xfs_filblks_t len, int flags,
                xfs_fsblock_t *firstblock, xfs_extlen_t total,
@@ -202,6 +199,13 @@ int        xfs_bmap_shift_extents(struct xfs_trans *tp, struct xfs_inode *ip,
                struct xfs_defer_ops *dfops, enum shift_direction direction,
                int num_exts);
 int    xfs_bmap_split_extent(struct xfs_inode *ip, xfs_fileoff_t split_offset);
+struct xfs_bmbt_rec_host *
+       xfs_bmap_search_extents(struct xfs_inode *ip, xfs_fileoff_t bno,
+               int fork, int *eofp, xfs_extnum_t *lastxp,
+               struct xfs_bmbt_irec *gotp, struct xfs_bmbt_irec *prevp);
+int    xfs_bmapi_reserve_delalloc(struct xfs_inode *ip, xfs_fileoff_t aoff,
+               xfs_filblks_t len, struct xfs_bmbt_irec *got,
+               struct xfs_bmbt_irec *prev, xfs_extnum_t *lastx, int eof);
 
 struct xfs_bmbt_rec_host *
        xfs_bmap_search_extents(struct xfs_inode *ip, xfs_fileoff_t bno,