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author | Jan Kara <jack@suse.cz> | 2016-03-09 23:11:13 -0500 |
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committer | Theodore Ts'o <tytso@mit.edu> | 2016-03-09 23:11:13 -0500 |
commit | 2d90c160e5f1d784e180f1e1458d56eee4d7f4f4 (patch) | |
tree | 883dc6e8433bbe315fa8fce00154d51ac52b3dd7 /fs/ext4/inode.c | |
parent | e3fb8eb14eafd2847c04cf48b52a705c36f4db98 (diff) | |
download | op-kernel-dev-2d90c160e5f1d784e180f1e1458d56eee4d7f4f4.zip op-kernel-dev-2d90c160e5f1d784e180f1e1458d56eee4d7f4f4.tar.gz |
ext4: more efficient SEEK_DATA implementation
Using SEEK_DATA in a huge sparse file can easily lead to sotflockups as
ext4_seek_data() iterates hole block-by-block. Fix the problem by using
returned hole size from ext4_map_blocks() and thus skip the hole in one
go.
Update also SEEK_HOLE implementation to follow the same pattern as
SEEK_DATA to make future maintenance easier.
Furthermore we add cond_resched() to both ext4_seek_data() and
ext4_seek_hole() to avoid softlockups in case evil user creates huge
fragmented file and we have to go through lots of extents.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/ext4/inode.c')
-rw-r--r-- | fs/ext4/inode.c | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index fddc6dd..ce2c4c6 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -5596,3 +5596,70 @@ int ext4_filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) return err; } + +/* + * Find the first extent at or after @lblk in an inode that is not a hole. + * Search for @map_len blocks at most. The extent is returned in @result. + * + * The function returns 1 if we found an extent. The function returns 0 in + * case there is no extent at or after @lblk and in that case also sets + * @result->es_len to 0. In case of error, the error code is returned. + */ +int ext4_get_next_extent(struct inode *inode, ext4_lblk_t lblk, + unsigned int map_len, struct extent_status *result) +{ + struct ext4_map_blocks map; + struct extent_status es = {}; + int ret; + + map.m_lblk = lblk; + map.m_len = map_len; + + /* + * For non-extent based files this loop may iterate several times since + * we do not determine full hole size. + */ + while (map.m_len > 0) { + ret = ext4_map_blocks(NULL, inode, &map, 0); + if (ret < 0) + return ret; + /* There's extent covering m_lblk? Just return it. */ + if (ret > 0) { + int status; + + ext4_es_store_pblock(result, map.m_pblk); + result->es_lblk = map.m_lblk; + result->es_len = map.m_len; + if (map.m_flags & EXT4_MAP_UNWRITTEN) + status = EXTENT_STATUS_UNWRITTEN; + else + status = EXTENT_STATUS_WRITTEN; + ext4_es_store_status(result, status); + return 1; + } + ext4_es_find_delayed_extent_range(inode, map.m_lblk, + map.m_lblk + map.m_len - 1, + &es); + /* Is delalloc data before next block in extent tree? */ + if (es.es_len && es.es_lblk < map.m_lblk + map.m_len) { + ext4_lblk_t offset = 0; + + if (es.es_lblk < lblk) + offset = lblk - es.es_lblk; + result->es_lblk = es.es_lblk + offset; + ext4_es_store_pblock(result, + ext4_es_pblock(&es) + offset); + result->es_len = es.es_len - offset; + ext4_es_store_status(result, ext4_es_status(&es)); + + return 1; + } + /* There's a hole at m_lblk, advance us after it */ + map.m_lblk += map.m_len; + map_len -= map.m_len; + map.m_len = map_len; + cond_resched(); + } + result->es_len = 0; + return 0; +} |