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ext4: get rid of EXT4_GET_BLOCKS_NO_LOCK flag

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When dioread_nolock mode is enabled, we grab i_data_sem in
ext4_ext_direct_IO() and therefore we need to instruct _ext4_get_block()
not to grab i_data_sem again using EXT4_GET_BLOCKS_NO_LOCK. However
holding i_data_sem over overwrite direct IO isn't needed these days. We
have exclusion against truncate / hole punching because we increase
i_dio_count under i_mutex in ext4_ext_direct_IO() so once
ext4_file_write_iter() verifies blocks are allocated & written, they are
guaranteed to stay so during the whole direct IO even after we drop
i_mutex.

So we can just remove this locking abuse and the no longer necessary
EXT4_GET_BLOCKS_NO_LOCK flag.

Signed-off-by: Jan Kara <jack@suse.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Jan Kara
2015-12-07 15:04:57 -05:00
committed by Theodore Ts'o
parent e74031fd7e
commit 2dcba4781f
3 changed files with 22 additions and 28 deletions
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4
fs/ext4/ext4.h
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@@ -555,10 +555,8 @@ enum {
#define EXT4_GET_BLOCKS_NO_NORMALIZE 0x0040
/* Request will not result in inode size update (user for fallocate) */
#define EXT4_GET_BLOCKS_KEEP_SIZE 0x0080
/* Do not take i_data_sem locking in ext4_map_blocks */
#define EXT4_GET_BLOCKS_NO_LOCK 0x0100
/* Convert written extents to unwritten */
#define EXT4_GET_BLOCKS_CONVERT_UNWRITTEN 0x0200
#define EXT4_GET_BLOCKS_CONVERT_UNWRITTEN 0x0100
/*
* The bit position of these flags must not overlap with any of the