On Thu 19-06-14 17:37:08, Lukas Czerner wrote:
> Currently punch hole code on files with direct/indirect mapping has some
> problems which may lead to a data loss. For example (from Jan Kara):
>
> fallocate -n -p 10240000 4096
>
> will punch the range 10240000 - 12632064 instead of the range 1024000 -
> 10244096.
>
> Also the code is a bit weird and it's not using infrastructure provided
> by indirect.c, but rather creating it's own way.
>
> This patch fixes the issues as well as making the operation to run 4
> times faster from my testing (punching out 60GB file). It uses similar
> approach used in ext4_ind_truncate() which takes advantage of
> ext4_free_branches() function.
>
> Also rename the ext4_free_hole_blocks() to something more sensible, like
> the equivalent we have for extent mapped files. Call it
> ext4_ind_remove_space().
>
> This has been tested mostly with fsx and some xfstests which are testing
> punch hole but does not require unwritten extents which are not
> supported with direct/indirect mapping. Not problems showed up even with
> 1024k block size.
Hum, so I agree current code could use more of the truncate
infrastructure and be faster (especially the all_zeroes() checks are
presumably rather expensive) but frankly I find your version harder to read
than the original code was :-|. I'll try to read your code again with fresh
mind and either decide it's good enough that I can give my reviewed-by or
I can try to come up with something simpler...
Honza
> CC: [email protected]
> Signed-off-by: Lukas Czerner <[email protected]>
> ---
> fs/ext4/ext4.h | 4 +-
> fs/ext4/indirect.c | 277
> +++++++++++++++++++++++++++++++++++++++--------------
> fs/ext4/inode.c | 2 +-
> 3 files changed, 207 insertions(+), 76 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 1479e2a..22113a73 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -2145,8 +2145,8 @@ extern ssize_t ext4_ind_direct_IO(int rw, struct kiocb
> *iocb,
> extern int ext4_ind_calc_metadata_amount(struct inode *inode, sector_t
> lblock);
> extern int ext4_ind_trans_blocks(struct inode *inode, int nrblocks);
> extern void ext4_ind_truncate(handle_t *, struct inode *inode);
> -extern int ext4_free_hole_blocks(handle_t *handle, struct inode *inode,
> - ext4_lblk_t first, ext4_lblk_t stop);
> +extern int ext4_ind_remove_space(handle_t *handle, struct inode *inode,
> + ext4_lblk_t start, ext4_lblk_t end);
>
> /* ioctl.c */
> extern long ext4_ioctl(struct file *, unsigned int, unsigned long);
> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
> index 594009f..adae538 100644
> --- a/fs/ext4/indirect.c
> +++ b/fs/ext4/indirect.c
> @@ -1291,89 +1291,220 @@ do_indirects:
> }
> }
>
> -static int free_hole_blocks(handle_t *handle, struct inode *inode,
> - struct buffer_head *parent_bh, __le32 *i_data,
> - int level, ext4_lblk_t first,
> - ext4_lblk_t count, int max)
> +/**
> + * ext4_ind_remove_space - remove space from the range
> + * @handle: JBD handle for this transaction
> + * @inode: inode we are dealing with
> + * @start: First block to remove
> + * @end: One block after the last block to remove (exclusive)
> + *
> + * Free the blocks in the defined range (end is exclusive endpoint of
> + * range). This is used by ext4_punch_hole().
> + */
> +int ext4_ind_remove_space(handle_t *handle, struct inode *inode,
> + ext4_lblk_t start, ext4_lblk_t end)
> {
> - struct buffer_head *bh = NULL;
> + struct ext4_inode_info *ei = EXT4_I(inode);
> + __le32 *i_data = ei->i_data;
> int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
> - int ret = 0;
> - int i, inc;
> - ext4_lblk_t offset;
> - __le32 blk;
> -
> - inc = 1 << ((EXT4_BLOCK_SIZE_BITS(inode->i_sb) - 2) * level);
> - for (i = 0, offset = 0; i < max; i++, i_data++, offset += inc) {
> - if (offset >= count + first)
> - break;
> - if (*i_data == 0 || (offset + inc) <= first)
> - continue;
> - blk = *i_data;
> - if (level > 0) {
> - ext4_lblk_t first2;
> - bh = sb_bread(inode->i_sb, le32_to_cpu(blk));
> - if (!bh) {
> - EXT4_ERROR_INODE_BLOCK(inode, le32_to_cpu(blk),
> - "Read failure");
> - return -EIO;
> + ext4_lblk_t offsets[4], offsets2[4];
> + Indirect chain[4], chain2[4];
> + Indirect *partial, *partial2;
> + ext4_lblk_t max_block;
> + __le32 nr = 0, nr2 = 0;
> + int n = 0, n2 = 0;
> + unsigned blocksize = inode->i_sb->s_blocksize;
> +
> + max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
> + >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
> + if (end >= max_block)
> + end = max_block;
> + if ((start >= end) || (start > max_block))
> + return 0;
> +
> + n = ext4_block_to_path(inode, start, offsets, NULL);
> + n2 = ext4_block_to_path(inode, end, offsets2, NULL);
> +
> + BUG_ON(n > n2);
> +
> + if ((n == 1) && (n == n2)) {
> + /* We're punching only within direct block range */
> + ext4_free_data(handle, inode, NULL, i_data + offsets[0],
> + i_data + offsets2[0]);
> + return 0;
> + } else if (n2 > n) {
> + /*
> + * Start and end are on a different levels so we're going to
> + * free partial block at start, and partial block at end of
> + * the range. If there are some levels in between then
> + * do_indirects label will take care of that.
> + */
> +
> + if (n == 1) {
> + /*
> + * Start is at the direct block level, free
> + * everything to the end of the level.
> + */
> + ext4_free_data(handle, inode, NULL, i_data + offsets[0],
> + i_data + EXT4_NDIR_BLOCKS);
> + goto end_range;
> + }
> +
> +
> + partial = ext4_find_shared(inode, n, offsets, chain, &nr);
> + if (nr) {
> + if (partial == chain) {
> + /* Shared branch grows from the inode */
> + ext4_free_branches(handle, inode, NULL,
> + &nr, &nr+1, (chain+n-1) - partial);
> + *partial->p = 0;
> + } else {
> + /* Shared branch grows from an indirect block */
> + BUFFER_TRACE(partial->bh, "get_write_access");
> + ext4_free_branches(handle, inode, partial->bh,
> + partial->p,
> + partial->p+1, (chain+n-1) - partial);
> }
> - first2 = (first > offset) ? first - offset : 0;
> - ret = free_hole_blocks(handle, inode, bh,
> - (__le32 *)bh->b_data, level - 1,
> - first2, count - offset,
> - inode->i_sb->s_blocksize >> 2);
> - if (ret) {
> - brelse(bh);
> - goto err;
> + }
> +
> + /*
> + * Clear the ends of indirect blocks on the shared branch
> + * at the start of the range
> + */
> + while (partial > chain) {
> + ext4_free_branches(handle, inode, partial->bh,
> + partial->p + 1,
> + (__le32 *)partial->bh->b_data+addr_per_block,
> + (chain+n-1) - partial);
> + BUFFER_TRACE(partial->bh, "call brelse");
> + brelse(partial->bh);
> + partial--;
> + }
> +
> +end_range:
> + partial2 = ext4_find_shared(inode, n2, offsets2, chain2, &nr2);
> + if (nr2) {
> + if (partial2 == chain2) {
> + /*
> + * Remember, end is exclusive so here we're at
> + * the start of the next level we're not going
> + * to free. Everything was covered by the start
> + * of the range.
> + */
> + return 0;
> + } else {
> + /* Shared branch grows from an indirect block */
> + partial2--;
> }
> + } else {
> + /*
> + * ext4_find_shared returns Indirect structure which
> + * points to the last element which should not be
> + * removed by truncate. But this is end of the range
> + * in punch_hole so we need to point to the next element
> + */
> + partial2->p++;
> }
> - if (level == 0 ||
> - (bh && all_zeroes((__le32 *)bh->b_data,
> - (__le32 *)bh->b_data + addr_per_block))) {
> - ext4_free_data(handle, inode, parent_bh, &blk, &blk+1);
> - *i_data = 0;
> +
> + /*
> + * Clear the ends of indirect blocks on the shared branch
> + * at the end of the range
> + */
> + while (partial2 > chain2) {
> + ext4_free_branches(handle, inode, partial2->bh,
> + (__le32 *)partial2->bh->b_data,
> + partial2->p,
> + (chain2+n2-1) - partial2);
> + BUFFER_TRACE(partial2->bh, "call brelse");
> + brelse(partial2->bh);
> + partial2--;
> }
> - brelse(bh);
> - bh = NULL;
> + goto do_indirects;
> }
>
> -err:
> - return ret;
> -}
> -
> -int ext4_free_hole_blocks(handle_t *handle, struct inode *inode,
> - ext4_lblk_t first, ext4_lblk_t stop)
> -{
> - int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
> - int level, ret = 0;
> - int num = EXT4_NDIR_BLOCKS;
> - ext4_lblk_t count, max = EXT4_NDIR_BLOCKS;
> - __le32 *i_data = EXT4_I(inode)->i_data;
> -
> - count = stop - first;
> - for (level = 0; level < 4; level++, max *= addr_per_block) {
> - if (first < max) {
> - ret = free_hole_blocks(handle, inode, NULL, i_data,
> - level, first, count, num);
> - if (ret)
> - goto err;
> - if (count > max - first)
> - count -= max - first;
> - else
> - break;
> - first = 0;
> - } else {
> - first -= max;
> + /* Punch happened within the same level (n == n2) */
> + partial = ext4_find_shared(inode, n, offsets, chain, &nr);
> + partial2 = ext4_find_shared(inode, n2, offsets2, chain2, &nr2);
> + /*
> + * ext4_find_shared returns Indirect structure which
> + * points to the last element which should not be
> + * removed by truncate. But this is end of the range
> + * in punch_hole so we need to point to the next element
> + */
> + partial2->p++;
> + while ((partial > chain) || (partial2 > chain2)) {
> + /* We're at the same block, so we're almost finished */
> + if ((partial->bh && partial2->bh) &&
> + (partial->bh->b_blocknr == partial2->bh->b_blocknr)) {
> + if ((partial > chain) && (partial2 > chain2)) {
> + ext4_free_branches(handle, inode, partial->bh,
> + partial->p + 1,
> + partial2->p,
> + (chain+n-1) - partial);
> + BUFFER_TRACE(partial->bh, "call brelse");
> + brelse(partial->bh);
> + BUFFER_TRACE(partial2->bh, "call brelse");
> + brelse(partial2->bh);
> + }
> + return 0;
> }
> - i_data += num;
> - if (level == 0) {
> - num = 1;
> - max = 1;
> + /*
> + * Clear the ends of indirect blocks on the shared branch
> + * at the start of the range
> + */
> + if (partial > chain) {
> + ext4_free_branches(handle, inode, partial->bh,
> + partial->p + 1,
> + (__le32 *)partial->bh->b_data+addr_per_block,
> + (chain+n-1) - partial);
> + BUFFER_TRACE(partial->bh, "call brelse");
> + brelse(partial->bh);
> + partial--;
> + }
> + /*
> + * Clear the ends of indirect blocks on the shared branch
> + * at the end of the range
> + */
> + if (partial2 > chain2) {
> + ext4_free_branches(handle, inode, partial2->bh,
> + (__le32 *)partial2->bh->b_data,
> + partial2->p,
> + (chain2+n-1) - partial2);
> + BUFFER_TRACE(partial2->bh, "call brelse");
> + brelse(partial2->bh);
> + partial2--;
> }
> }
>
> -err:
> - return ret;
> +do_indirects:
> + /* Kill the remaining (whole) subtrees */
> + switch (offsets[0]) {
> + default:
> + if (++n >= n2)
> + return 0;
> + nr = i_data[EXT4_IND_BLOCK];
> + if (nr) {
> + ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 1);
> + i_data[EXT4_IND_BLOCK] = 0;
> + }
> + case EXT4_IND_BLOCK:
> + if (++n >= n2)
> + return 0;
> + nr = i_data[EXT4_DIND_BLOCK];
> + if (nr) {
> + ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 2);
> + i_data[EXT4_DIND_BLOCK] = 0;
> + }
> + case EXT4_DIND_BLOCK:
> + if (++n >= n2)
> + return 0;
> + nr = i_data[EXT4_TIND_BLOCK];
> + if (nr) {
> + ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 3);
> + i_data[EXT4_TIND_BLOCK] = 0;
> + }
> + case EXT4_TIND_BLOCK:
> + ;
> + }
> + return 0;
> }
> -
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 7fcd68e..a5adc09 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3626,7 +3626,7 @@ int ext4_punch_hole(struct inode *inode, loff_t offset,
> loff_t length)
> ret = ext4_ext_remove_space(inode, first_block,
> stop_block - 1);
> else
> - ret = ext4_free_hole_blocks(handle, inode, first_block,
> + ret = ext4_ind_remove_space(handle, inode, first_block,
> stop_block);
>
> up_write(&EXT4_I(inode)->i_data_sem);
> --
> 1.8.3.1
>
--
Jan Kara <[email protected]>
SUSE Labs, CR
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