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writeback: fix WB_SYNC_NONE writeback from umount

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When umount calls sync_filesystem(), we first do a WB_SYNC_NONE
writeback to kick off writeback of pending dirty inodes, then follow
that up with a WB_SYNC_ALL to wait for it. Since umount already holds
the sb s_umount mutex, WB_SYNC_NONE ends up doing nothing and all
writeback happens as WB_SYNC_ALL. This can greatly slow down umount,
since WB_SYNC_ALL writeback is a data integrity operation and thus
a bigger hammer than simple WB_SYNC_NONE. For barrier aware file systems
it's a lot slower.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe
2010-05-17 12:55:07 +02:00
parent 69b62d01ec
commit e913fc825d
5 changed files with 51 additions and 15 deletions
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10
include/linux/writeback.h
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@@ -65,6 +65,15 @@ struct writeback_control {
* so we use a single control to update them
*/
unsigned no_nrwrite_index_update:1;
/*
* For WB_SYNC_ALL, the sb must always be pinned. For WB_SYNC_NONE,
* the writeback code will pin the sb for the caller. However,
* for eg umount, the caller does WB_SYNC_NONE but already has
* the sb pinned. If the below is set, caller already has the
* sb pinned.
*/
unsigned sb_pinned:1;
};
/*
@@ -73,6 +82,7 @@ struct writeback_control {
struct bdi_writeback;
int inode_wait(void *);
void writeback_inodes_sb(struct super_block *);
void writeback_inodes_sb_locked(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);