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libext2fs: try to always use PUNCH_HOLE for unix_discard

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Now that block devices support PUNCH_HOLE via fallocate, refactor the
unix_discard code into a helper that will always try to use it.  For
block devices we can fall back to BLKDISCARD, but we prefer to use
fallocate because it will always invalidate the page cache of the zeroed
region.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Darrick J. Wong 2018-08-28 16:38:07 -07:00 committed by Theodore Ts'o
parent 3f6a9786d7
commit bcca9876a3
1 changed files with 36 additions and 25 deletions
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61
lib/ext2fs/unix_io.c
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@ -1081,6 +1081,38 @@ static errcode_t unix_set_option(io_channel channel, const char *option,
#define BLKDISCARD _IO(0x12,119)
#endif
/*
* Try a PUNCH_HOLE to unmap blocks, then BLKDISCARD if that doesn't work.
* We prefer PUNCH_HOLE because it invalidates the page cache, even on block
* devices.
*/
static int __unix_discard(int fd, int is_bdev, off_t offset, off_t len)
{
#ifdef BLKDISCARD
__u64 range[2];
#endif
int ret = -1;
#if defined(HAVE_FALLOCATE) && defined(FALLOC_FL_PUNCH_HOLE) && defined(FALLOC_FL_KEEP_SIZE)
ret = fallocate(fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
offset, len);
if (ret == 0)
return 0;
#endif
#ifdef BLKDISCARD
if (is_bdev) {
range[0] = (__u64)offset;
range[1] = (__u64)len;
ret = ioctl(fd, BLKDISCARD, &range);
if (ret == 0)
return 0;
}
#endif
errno = EOPNOTSUPP;
return ret;
}
static errcode_t unix_discard(io_channel channel, unsigned long long block,
unsigned long long count)
{
@ -1091,31 +1123,10 @@ static errcode_t unix_discard(io_channel channel, unsigned long long block,
data = (struct unix_private_data *) channel->private_data;
EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
if (channel->flags & CHANNEL_FLAGS_BLOCK_DEVICE) {
#ifdef BLKDISCARD
__u64 range[2];
range[0] = (__u64)(block) * channel->block_size + data->offset;
range[1] = (__u64)(count) * channel->block_size;
ret = ioctl(data->dev, BLKDISCARD, &range);
#else
goto unimplemented;
#endif
} else {
#if defined(HAVE_FALLOCATE) && defined(FALLOC_FL_PUNCH_HOLE)
/*
* If we are not on block device, try to use punch hole
* to reclaim free space.
*/
ret = fallocate(data->dev,
FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
(off_t)(block) * channel->block_size + data->offset,
(off_t)(count) * channel->block_size);
#else
goto unimplemented;
#endif
}
ret = __unix_discard(data->dev,
(channel->flags & CHANNEL_FLAGS_BLOCK_DEVICE),
(off_t)(block) * channel->block_size + data->offset,
(off_t)(count) * channel->block_size);
if (ret < 0) {
if (errno == EOPNOTSUPP)
goto unimplemented;