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superblock: add filesystem shrinker operations

Now we have a per-superblock shrinker implementation, we can add a
filesystem specific callout to it to allow filesystem internal
caches to be shrunk by the superblock shrinker.

Rather than perpetuate the multipurpose shrinker callback API (i.e.
nr_to_scan == 0 meaning "tell me how many objects freeable in the
cache), two operations will be added. The first will return the
number of objects that are freeable, the second is the actual
shrinker call.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Dave Chinner 2011-07-08 14:14:44 +10:00 committed by Al Viro
parent 4f8c19fdf3
commit 0e1fdafd93
3 changed files with 50 additions and 11 deletions

View File

@ -229,6 +229,8 @@ struct super_operations {
ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
int (*nr_cached_objects)(struct super_block *);
void (*free_cached_objects)(struct super_block *, int);
};
All methods are called without any locks being held, unless otherwise
@ -301,6 +303,20 @@ or bottom half).
quota_write: called by the VFS to write to filesystem quota file.
nr_cached_objects: called by the sb cache shrinking function for the
filesystem to return the number of freeable cached objects it contains.
Optional.
free_cache_objects: called by the sb cache shrinking function for the
filesystem to scan the number of objects indicated to try to free them.
Optional, but any filesystem implementing this method needs to also
implement ->nr_cached_objects for it to be called correctly.
We can't do anything with any errors that the filesystem might
encountered, hence the void return type. This will never be called if
the VM is trying to reclaim under GFP_NOFS conditions, hence this
method does not need to handle that situation itself.
Whoever sets up the inode is responsible for filling in the "i_op" field. This
is a pointer to a "struct inode_operations" which describes the methods that
can be performed on individual inodes.

View File

@ -48,7 +48,8 @@ DEFINE_SPINLOCK(sb_lock);
static int prune_super(struct shrinker *shrink, struct shrink_control *sc)
{
struct super_block *sb;
int count;
int fs_objects = 0;
int total_objects;
sb = container_of(shrink, struct super_block, s_shrink);
@ -62,22 +63,42 @@ static int prune_super(struct shrinker *shrink, struct shrink_control *sc)
if (!grab_super_passive(sb))
return -1;
if (sb->s_op && sb->s_op->nr_cached_objects)
fs_objects = sb->s_op->nr_cached_objects(sb);
total_objects = sb->s_nr_dentry_unused +
sb->s_nr_inodes_unused + fs_objects + 1;
if (sc->nr_to_scan) {
/* proportion the scan between the two caches */
int total;
int dentries;
int inodes;
total = sb->s_nr_dentry_unused + sb->s_nr_inodes_unused + 1;
count = (sc->nr_to_scan * sb->s_nr_dentry_unused) / total;
/* proportion the scan between the caches */
dentries = (sc->nr_to_scan * sb->s_nr_dentry_unused) /
total_objects;
inodes = (sc->nr_to_scan * sb->s_nr_inodes_unused) /
total_objects;
if (fs_objects)
fs_objects = (sc->nr_to_scan * fs_objects) /
total_objects;
/*
* prune the dcache first as the icache is pinned by it, then
* prune the icache, followed by the filesystem specific caches
*/
prune_dcache_sb(sb, dentries);
prune_icache_sb(sb, inodes);
/* prune dcache first as icache is pinned by it */
prune_dcache_sb(sb, count);
prune_icache_sb(sb, sc->nr_to_scan - count);
if (fs_objects && sb->s_op->free_cached_objects) {
sb->s_op->free_cached_objects(sb, fs_objects);
fs_objects = sb->s_op->nr_cached_objects(sb);
}
total_objects = sb->s_nr_dentry_unused +
sb->s_nr_inodes_unused + fs_objects;
}
count = ((sb->s_nr_dentry_unused + sb->s_nr_inodes_unused) / 100)
* sysctl_vfs_cache_pressure;
total_objects = (total_objects / 100) * sysctl_vfs_cache_pressure;
drop_super(sb);
return count;
return total_objects;
}
/**

View File

@ -1655,6 +1655,8 @@ struct super_operations {
ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
#endif
int (*bdev_try_to_free_page)(struct super_block*, struct page*, gfp_t);
int (*nr_cached_objects)(struct super_block *);
void (*free_cached_objects)(struct super_block *, int);
};
/*