| Message ID | 20200524171709.GI8230@magnolia (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | None | expand |
On Sun, May 24, 2020 at 10:17:09AM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong <darrick.wong@oracle.com> > > Refactor xfs_iomap_prealloc_size to be the function that dynamically > computes the per-file preallocation size by moving the allocsize= case > to the caller. Break up the huge comment preceding the function to > annotate the relevant parts of the code, and remove the impossible > check_writeio case. > > Suggested-by: Christoph Hellwig <hch@infradead.org> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> > Reviewed-by: Christoph Hellwig <hch@lst.de> > --- > v2: minor rebase due to changes in previous patch > --- Reviewed-by: Brian Foster <bfoster@redhat.com> > fs/xfs/xfs_iomap.c | 83 ++++++++++++++++++++++------------------------------ > 1 file changed, 35 insertions(+), 48 deletions(-) > > diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c > index e74a8c2c94ce..b9a8c3798e08 100644 > --- a/fs/xfs/xfs_iomap.c > +++ b/fs/xfs/xfs_iomap.c > @@ -352,22 +352,10 @@ xfs_quota_calc_throttle( > } > > /* > - * If we are doing a write at the end of the file and there are no allocations > - * past this one, then extend the allocation out to the file system's write > - * iosize. > - * > * If we don't have a user specified preallocation size, dynamically increase > * the preallocation size as the size of the file grows. Cap the maximum size > * at a single extent or less if the filesystem is near full. The closer the > - * filesystem is to full, the smaller the maximum prealocation. > - * > - * As an exception we don't do any preallocation at all if the file is smaller > - * than the minimum preallocation and we are using the default dynamic > - * preallocation scheme, as it is likely this is the only write to the file that > - * is going to be done. > - * > - * We clean up any extra space left over when the file is closed in > - * xfs_inactive(). > + * filesystem is to being full, the smaller the maximum preallocation. > */ > STATIC xfs_fsblock_t > xfs_iomap_prealloc_size( > @@ -389,41 +377,28 @@ xfs_iomap_prealloc_size( > int shift = 0; > int qshift = 0; > > - if (offset + count <= XFS_ISIZE(ip)) > - return 0; > - > - if (!(mp->m_flags & XFS_MOUNT_ALLOCSIZE) && > - (XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_allocsize_blocks))) > + /* > + * As an exception we don't do any preallocation at all if the file is > + * smaller than the minimum preallocation and we are using the default > + * dynamic preallocation scheme, as it is likely this is the only write > + * to the file that is going to be done. > + */ > + if (XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_allocsize_blocks)) > return 0; > > /* > - * If an explicit allocsize is set, the file is small, or we > - * are writing behind a hole, then use the minimum prealloc: > + * Use the minimum preallocation size for small files or if we are > + * writing right after a hole. > */ > - if ((mp->m_flags & XFS_MOUNT_ALLOCSIZE) || > - XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_dalign) || > + if (XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_dalign) || > !xfs_iext_prev_extent(ifp, &ncur, &prev) || > prev.br_startoff + prev.br_blockcount < offset_fsb) > return mp->m_allocsize_blocks; > > /* > - * Determine the initial size of the preallocation. We are beyond the > - * current EOF here, but we need to take into account whether this is > - * a sparse write or an extending write when determining the > - * preallocation size. Hence we need to look up the extent that ends > - * at the current write offset and use the result to determine the > - * preallocation size. > - * > - * If the extent is a hole, then preallocation is essentially disabled. > - * Otherwise we take the size of the preceding data extents as the basis > - * for the preallocation size. Note that we don't care if the previous > - * extents are written or not. > - * > - * If the size of the extents is greater than half the maximum extent > - * length, then use the current offset as the basis. This ensures that > - * for large files the preallocation size always extends to MAXEXTLEN > - * rather than falling short due to things like stripe unit/width > - * alignment of real extents. > + * Take the size of the preceding data extents as the basis for the > + * preallocation size. Note that we don't care if the previous extents > + * are written or not. > */ > plen = prev.br_blockcount; > while (xfs_iext_prev_extent(ifp, &ncur, &got)) { > @@ -435,19 +410,25 @@ xfs_iomap_prealloc_size( > plen += got.br_blockcount; > prev = got; > } > + > + /* > + * If the size of the extents is greater than half the maximum extent > + * length, then use the current offset as the basis. This ensures that > + * for large files the preallocation size always extends to MAXEXTLEN > + * rather than falling short due to things like stripe unit/width > + * alignment of real extents. > + */ > alloc_blocks = plen * 2; > if (alloc_blocks > MAXEXTLEN) > alloc_blocks = XFS_B_TO_FSB(mp, offset); > - if (!alloc_blocks) > - goto check_writeio; > qblocks = alloc_blocks; > > /* > * MAXEXTLEN is not a power of two value but we round the prealloc down > * to the nearest power of two value after throttling. To prevent the > - * round down from unconditionally reducing the maximum supported prealloc > - * size, we round up first, apply appropriate throttling, round down and > - * cap the value to MAXEXTLEN. > + * round down from unconditionally reducing the maximum supported > + * prealloc size, we round up first, apply appropriate throttling, > + * round down and cap the value to MAXEXTLEN. > */ > alloc_blocks = XFS_FILEOFF_MIN(roundup_pow_of_two(MAXEXTLEN), > alloc_blocks); > @@ -508,7 +489,6 @@ xfs_iomap_prealloc_size( > */ > while (alloc_blocks && alloc_blocks >= freesp) > alloc_blocks >>= 4; > -check_writeio: > if (alloc_blocks < mp->m_allocsize_blocks) > alloc_blocks = mp->m_allocsize_blocks; > trace_xfs_iomap_prealloc_size(ip, alloc_blocks, shift, > @@ -975,9 +955,16 @@ xfs_buffered_write_iomap_begin( > if (error) > goto out_unlock; > > - if (eof) { > - prealloc_blocks = xfs_iomap_prealloc_size(ip, allocfork, offset, > - count, &icur); > + if (eof && offset + count > XFS_ISIZE(ip)) { > + /* > + * Determine the initial size of the preallocation. > + * We clean up any extra preallocation when the file is closed. > + */ > + if (mp->m_flags & XFS_MOUNT_ALLOCSIZE) > + prealloc_blocks = mp->m_allocsize_blocks; > + else > + prealloc_blocks = xfs_iomap_prealloc_size(ip, allocfork, > + offset, count, &icur); > if (prealloc_blocks) { > xfs_extlen_t align; > xfs_off_t end_offset; >
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c index e74a8c2c94ce..b9a8c3798e08 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -352,22 +352,10 @@ xfs_quota_calc_throttle( } /* - * If we are doing a write at the end of the file and there are no allocations - * past this one, then extend the allocation out to the file system's write - * iosize. - * * If we don't have a user specified preallocation size, dynamically increase * the preallocation size as the size of the file grows. Cap the maximum size * at a single extent or less if the filesystem is near full. The closer the - * filesystem is to full, the smaller the maximum prealocation. - * - * As an exception we don't do any preallocation at all if the file is smaller - * than the minimum preallocation and we are using the default dynamic - * preallocation scheme, as it is likely this is the only write to the file that - * is going to be done. - * - * We clean up any extra space left over when the file is closed in - * xfs_inactive(). + * filesystem is to being full, the smaller the maximum preallocation. */ STATIC xfs_fsblock_t xfs_iomap_prealloc_size( @@ -389,41 +377,28 @@ xfs_iomap_prealloc_size( int shift = 0; int qshift = 0; - if (offset + count <= XFS_ISIZE(ip)) - return 0; - - if (!(mp->m_flags & XFS_MOUNT_ALLOCSIZE) && - (XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_allocsize_blocks))) + /* + * As an exception we don't do any preallocation at all if the file is + * smaller than the minimum preallocation and we are using the default + * dynamic preallocation scheme, as it is likely this is the only write + * to the file that is going to be done. + */ + if (XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_allocsize_blocks)) return 0; /* - * If an explicit allocsize is set, the file is small, or we - * are writing behind a hole, then use the minimum prealloc: + * Use the minimum preallocation size for small files or if we are + * writing right after a hole. */ - if ((mp->m_flags & XFS_MOUNT_ALLOCSIZE) || - XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_dalign) || + if (XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_dalign) || !xfs_iext_prev_extent(ifp, &ncur, &prev) || prev.br_startoff + prev.br_blockcount < offset_fsb) return mp->m_allocsize_blocks; /* - * Determine the initial size of the preallocation. We are beyond the - * current EOF here, but we need to take into account whether this is - * a sparse write or an extending write when determining the - * preallocation size. Hence we need to look up the extent that ends - * at the current write offset and use the result to determine the - * preallocation size. - * - * If the extent is a hole, then preallocation is essentially disabled. - * Otherwise we take the size of the preceding data extents as the basis - * for the preallocation size. Note that we don't care if the previous - * extents are written or not. - * - * If the size of the extents is greater than half the maximum extent - * length, then use the current offset as the basis. This ensures that - * for large files the preallocation size always extends to MAXEXTLEN - * rather than falling short due to things like stripe unit/width - * alignment of real extents. + * Take the size of the preceding data extents as the basis for the + * preallocation size. Note that we don't care if the previous extents + * are written or not. */ plen = prev.br_blockcount; while (xfs_iext_prev_extent(ifp, &ncur, &got)) { @@ -435,19 +410,25 @@ xfs_iomap_prealloc_size( plen += got.br_blockcount; prev = got; } + + /* + * If the size of the extents is greater than half the maximum extent + * length, then use the current offset as the basis. This ensures that + * for large files the preallocation size always extends to MAXEXTLEN + * rather than falling short due to things like stripe unit/width + * alignment of real extents. + */ alloc_blocks = plen * 2; if (alloc_blocks > MAXEXTLEN) alloc_blocks = XFS_B_TO_FSB(mp, offset); - if (!alloc_blocks) - goto check_writeio; qblocks = alloc_blocks; /* * MAXEXTLEN is not a power of two value but we round the prealloc down * to the nearest power of two value after throttling. To prevent the - * round down from unconditionally reducing the maximum supported prealloc - * size, we round up first, apply appropriate throttling, round down and - * cap the value to MAXEXTLEN. + * round down from unconditionally reducing the maximum supported + * prealloc size, we round up first, apply appropriate throttling, + * round down and cap the value to MAXEXTLEN. */ alloc_blocks = XFS_FILEOFF_MIN(roundup_pow_of_two(MAXEXTLEN), alloc_blocks); @@ -508,7 +489,6 @@ xfs_iomap_prealloc_size( */ while (alloc_blocks && alloc_blocks >= freesp) alloc_blocks >>= 4; -check_writeio: if (alloc_blocks < mp->m_allocsize_blocks) alloc_blocks = mp->m_allocsize_blocks; trace_xfs_iomap_prealloc_size(ip, alloc_blocks, shift, @@ -975,9 +955,16 @@ xfs_buffered_write_iomap_begin( if (error) goto out_unlock; - if (eof) { - prealloc_blocks = xfs_iomap_prealloc_size(ip, allocfork, offset, - count, &icur); + if (eof && offset + count > XFS_ISIZE(ip)) { + /* + * Determine the initial size of the preallocation. + * We clean up any extra preallocation when the file is closed. + */ + if (mp->m_flags & XFS_MOUNT_ALLOCSIZE) + prealloc_blocks = mp->m_allocsize_blocks; + else + prealloc_blocks = xfs_iomap_prealloc_size(ip, allocfork, + offset, count, &icur); if (prealloc_blocks) { xfs_extlen_t align; xfs_off_t end_offset;