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ext4: implement allocation of pre-zeroed blocks 

DAX page fault path needs to get blocks that are pre-zeroed to avoid
races when two concurrent page faults happen in the same block of a
file. Implement support for this in ext4_map_blocks().

Signed-off-by: Jan Kara <jack@suse.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
hifive-unleashed-5.1
Jan Kara 2015-12-07 15:10:26 -05:00 committed by Theodore Ts'o
parent 53085fac02
commit c86d8db33a
4 changed files with 36 additions and 4 deletions
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4
fs/ext4/ext4.h
View File

@ -557,6 +557,10 @@ enum {
#define EXT4_GET_BLOCKS_KEEP_SIZE 0x0080
/* Convert written extents to unwritten */
#define EXT4_GET_BLOCKS_CONVERT_UNWRITTEN 0x0100
/* Write zeros to newly created written extents */
#define EXT4_GET_BLOCKS_ZERO 0x0200
#define EXT4_GET_BLOCKS_CREATE_ZERO (EXT4_GET_BLOCKS_CREATE |\
EXT4_GET_BLOCKS_ZERO)
/*
* The bit position of these flags must not overlap with any of the

8
fs/ext4/extents.c
View File

@ -4044,6 +4044,14 @@ ext4_ext_handle_unwritten_extents(handle_t *handle, struct inode *inode,
}
/* IO end_io complete, convert the filled extent to written */
if (flags & EXT4_GET_BLOCKS_CONVERT) {
if (flags & EXT4_GET_BLOCKS_ZERO) {
if (allocated > map->m_len)
allocated = map->m_len;
err = ext4_issue_zeroout(inode, map->m_lblk, newblock,
allocated);
if (err < 0)
goto out2;
}
ret = ext4_convert_unwritten_extents_endio(handle, inode, map,
ppath);
if (ret >= 0) {

25
fs/ext4/inode.c
View File

@ -636,6 +636,22 @@ found:
WARN_ON(1);
}
/*
* We have to zeroout blocks before inserting them into extent
* status tree. Otherwise someone could look them up there and
* use them before they are really zeroed.
*/
if (flags & EXT4_GET_BLOCKS_ZERO &&
map->m_flags & EXT4_MAP_MAPPED &&
map->m_flags & EXT4_MAP_NEW) {
ret = ext4_issue_zeroout(inode, map->m_lblk,
map->m_pblk, map->m_len);
if (ret) {
retval = ret;
goto out_sem;
}
}
/*
* If the extent has been zeroed out, we don't need to update
* extent status tree.
@ -643,7 +659,7 @@ found:
if ((flags & EXT4_GET_BLOCKS_PRE_IO) &&
ext4_es_lookup_extent(inode, map->m_lblk, &es)) {
if (ext4_es_is_written(&es))
goto has_zeroout;
goto out_sem;
}
status = map->m_flags & EXT4_MAP_UNWRITTEN ?
EXTENT_STATUS_UNWRITTEN : EXTENT_STATUS_WRITTEN;
@ -654,11 +670,13 @@ found:
status |= EXTENT_STATUS_DELAYED;
ret = ext4_es_insert_extent(inode, map->m_lblk, map->m_len,
map->m_pblk, status);
if (ret < 0)
if (ret < 0) {
retval = ret;
goto out_sem;
}
}
has_zeroout:
out_sem:
up_write((&EXT4_I(inode)->i_data_sem));
if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
ret = check_block_validity(inode, map);
@ -3083,6 +3101,7 @@ int ext4_get_block_dax(struct inode *inode, sector_t iblock,
struct buffer_head *bh_result, int create)
{
int flags = EXT4_GET_BLOCKS_PRE_IO | EXT4_GET_BLOCKS_UNWRIT_EXT;
if (create)
flags |= EXT4_GET_BLOCKS_CREATE;
ext4_debug("ext4_get_block_dax: inode %lu, create flag %d\n",

3
include/trace/events/ext4.h
View File

@ -42,7 +42,8 @@ struct extent_status;
{ EXT4_GET_BLOCKS_CONVERT, "CONVERT" }, \
{ EXT4_GET_BLOCKS_METADATA_NOFAIL, "METADATA_NOFAIL" }, \
{ EXT4_GET_BLOCKS_NO_NORMALIZE, "NO_NORMALIZE" }, \
{ EXT4_GET_BLOCKS_KEEP_SIZE, "KEEP_SIZE" })
{ EXT4_GET_BLOCKS_KEEP_SIZE, "KEEP_SIZE" }, \
{ EXT4_GET_BLOCKS_ZERO, "ZERO" })
#define show_mflags(flags) __print_flags(flags, "", \
{ EXT4_MAP_NEW, "N" }, \