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ext4: more efficient SEEK_DATA implementation

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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>
This commit is contained in:
Jan Kara
2016-03-09 23:11:13 -05:00
committed by Theodore Ts'o
parent e3fb8eb14e
commit 2d90c160e5
3 changed files with 106 additions and 61 deletions
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3
fs/ext4/ext4.h
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@@ -2546,6 +2546,9 @@ extern void ext4_da_update_reserve_space(struct inode *inode,
int used, int quota_claim);
extern int ext4_issue_zeroout(struct inode *inode, ext4_lblk_t lblk,
ext4_fsblk_t pblk, ext4_lblk_t len);
extern int ext4_get_next_extent(struct inode *inode, ext4_lblk_t lblk,
unsigned int map_len,
struct extent_status *result);
/* indirect.c */
extern int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,