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ext4: fix punch hole on files with indirect mapping 

commit 4f579ae7de560e5f449587a6c3f02594d53d4d51 upstream.

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.

Change-Id: I50cfdf1a688774674341fef9cb3b6ba65875e6af
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Lukas Czerner 2014-07-15 06:03:38 -04:00 committed by syphyr
parent 4bf9fddb6f
commit 252f1c5c18
3 changed files with 205 additions and 82 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
fs/ext4/ext4.h
View File

@ -2197,8 +2197,8 @@ 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);

281
fs/ext4/indirect.c
View File

@ -1300,97 +1300,220 @@ 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;
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;
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;
ext4_lblk_t count2;
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;
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;
}
if (first > offset) {
first2 = first - offset;
count2 = count;
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 {
first2 = 0;
count2 = count - (offset - first);
}
ret = free_hole_blocks(handle, inode, bh,
(__le32 *)bh->b_data, level - 1,
first2, count2,
inode->i_sb->s_blocksize >> 2);
if (ret) {
brelse(bh);
goto err;
/* 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);
}
}
if (level == 0 ||
(bh && all_zeroes((__le32 *)bh->b_data,
(__le32 *)bh->b_data + addr_per_block))) {
ext4_free_data(handle, inode, parent_bh,
i_data, i_data + 1);
/*
* 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--;
}
brelse(bh);
bh = NULL;
}
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;
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 {
first -= max;
/*
* 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++;
}
i_data += num;
if (level == 0) {
num = 1;
max = 1;
/*
* 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--;
}
goto do_indirects;
}
/* 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;
}
/*
* 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;
}

2
fs/ext4/inode.c
View File

@ -3811,7 +3811,7 @@ int ext4_punch_hole(struct file *file, 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);
ext4_discard_preallocations(inode);