On Fri, Aug 26, 2016 at 12:03:39PM -0400, Brian Foster wrote:
> On Fri, Aug 26, 2016 at 04:33:44PM +0200, Christoph Hellwig wrote:
> > On Thu, Aug 25, 2016 at 10:37:09AM -0400, Brian Foster wrote:
...
> > (we could potentially re-derive offset_fsb from offset if we don't
> > mind the inefficieny and recalculate maxbytes_fsb. This already
> > assumes mp is trivially derived from ip)
> >
> > and return
> >
> > alloc_blocks, end_fsb
> >
> > so the function would be quite a monster in terms of its calling
> > convention. Additionally we'd have the related by not qute the
> > same if blocks around XFS_MOUNT_DFLT_IOSIZE and the isize split
> > over two functions, which doesn't exactly help understanding
> > the flow.
> >
>
> Not quite sure I follow the last bit, but I don't necessarily think the
> whole thing has to be boxed into a helper to clean it up. E.g., I'd do
> something like the appended diff (compile tested only).
>
... and if the function signature is really an issue, trade off idx &
prev for a conditional base preallocation size (applies on top of the
previous diff):
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 45e5268..c748429 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -381,7 +381,7 @@ STATIC xfs_fsblock_t
xfs_iomap_prealloc_size(
struct xfs_inode *ip,
xfs_off_t offset,
- struct xfs_bmbt_irec *prev)
+ xfs_extlen_t base)
{
struct xfs_mount *mp = ip->i_mount;
int shift = 0;
@@ -406,8 +406,8 @@ xfs_iomap_prealloc_size(
* always extends to MAXEXTLEN rather than falling short due to things
* like stripe unit/width alignment of real extents.
*/
- if (prev->br_blockcount <= (MAXEXTLEN >> 1))
- alloc_blocks = prev->br_blockcount << 1;
+ if (base <= (MAXEXTLEN >> 1))
+ alloc_blocks = base << 1;
else
alloc_blocks = XFS_B_TO_FSB(mp, offset);
if (!alloc_blocks)
@@ -506,12 +506,10 @@ xfs_iomap_prealloc(
struct xfs_inode *ip,
loff_t offset,
loff_t count,
- xfs_extnum_t idx,
- struct xfs_bmbt_irec *prev)
+ xfs_extlen_t base)
{
struct xfs_mount *mp = ip->i_mount;
xfs_fsblock_t alloc_blocks;
- xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset);
if (offset + count <= XFS_ISIZE(ip))
return 0;
@@ -526,12 +524,11 @@ xfs_iomap_prealloc(
*/
if ((mp->m_flags & XFS_MOUNT_DFLT_IOSIZE) ||
XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_dalign) ||
- idx == 0 ||
- prev->br_startoff + prev->br_blockcount < offset_fsb)
+ !base)
alloc_blocks = mp->m_writeio_blocks;
else
alloc_blocks =
- xfs_iomap_prealloc_size(ip, offset, prev);
+ xfs_iomap_prealloc_size(ip, offset, base);
return alloc_blocks;
}
@@ -603,8 +600,15 @@ xfs_file_iomap_begin_delay(
end_fsb = orig_end_fsb =
min(XFS_B_TO_FSB(mp, offset + count), maxbytes_fsb);
- if (eof)
- prealloc = xfs_iomap_prealloc(ip, offset, count, idx, &prev);
+ if (eof) {
+ xfs_extlen_t base = 0;
+
+ /* use prev extent as base if contiguous */
+ if (idx > 0 &&
+ prev.br_startoff + prev.br_blockcount < offset_fsb)
+ base = prev.br_blockcount;
+ prealloc = xfs_iomap_prealloc(ip, offset, count, base);
+ }
if (prealloc) {
xfs_off_t aligned_offset;
xfs_extlen_t align;
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