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fs-writeback: Add helper function to start writeback if idle 

ext4, at least, would like to start pushing on writeback if it starts
to get close to ENOSPC when reserving worst-case blocks for delalloc
writes.  Writing out delalloc data will convert those worst-case
predictions into usually smaller actual usage, freeing up space
before we hit ENOSPC based on this speculation.

Thanks to Jens for the suggestion for the helper function,
& the naming help.

I've made the helper return status on whether writeback was
started even though I don't plan to use it in the ext4 patch;
it seems like it would be potentially useful to test this
in some cases.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Acked-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Eric Sandeen 2009-12-23 07:57:07 -05:00 committed by Theodore Ts'o
parent d3533d72e7
commit 17bd55d037
2 changed files with 18 additions and 0 deletions
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17
fs/fs-writeback.c
View File

@ -1186,6 +1186,23 @@ void writeback_inodes_sb(struct super_block *sb)
}
EXPORT_SYMBOL(writeback_inodes_sb);
/**
* writeback_inodes_sb_if_idle - start writeback if none underway
* @sb: the superblock
*
* Invoke writeback_inodes_sb if no writeback is currently underway.
* Returns 1 if writeback was started, 0 if not.
*/
int writeback_inodes_sb_if_idle(struct super_block *sb)
{
if (!writeback_in_progress(sb->s_bdi)) {
writeback_inodes_sb(sb);
return 1;
} else
return 0;
}
EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
/**
* sync_inodes_sb - sync sb inode pages
* @sb: the superblock

1
include/linux/writeback.h
View File

@ -70,6 +70,7 @@ struct writeback_control {
struct bdi_writeback;
int inode_wait(void *);
void writeback_inodes_sb(struct super_block *);
int writeback_inodes_sb_if_idle(struct super_block *);
void sync_inodes_sb(struct super_block *);
void writeback_inodes_wbc(struct writeback_control *wbc);
long wb_do_writeback(struct bdi_writeback *wb, int force_wait);