From: Artem Bityutskiy <artem.bityutskiy@xxxxxxxxxxxxxxx>
Currently FAT file-system maps the VFS "superblock" abstraction to the FSINFO
block. The FSINFO block contains non-essential data about the amount of free
clusters and the next free cluster. FAT file-system can always find out this
information by scanning the FAT table, but having it in the FSINFO block may
speed things up sometimes. So FAT file-system relies on the VFS superblock
write-out services to make sure the FSINFO block is written out to the media
from time to time.
The whole "superblock write-out" VFS infrastructure is served by the
'sync_supers()' kernel thread, which wakes up every 5 (by default) seconds and
writes out all dirty superblock using the '->write_super()' call-back. But the
problem with this thread is that it wastes power by waking up the system every
5 seconds no matter what. So we want to kill it completely and thus, we need to
make file-systems to stop using the '->write_super' VFS service, and then
remove it together with the kernel thread.
This patch switches the FAT FSINFO block management from
'->write_super()'/'->s_dirt' to 'fsinfo_inode'/'->write_inode'. Now, instead of
setting the 's_dirt' flag, we just mark the special 'fsinfo_inode' inode as
dirty and let VFS invoke the '->write_inode' call-back when needed, where we
write-out the FSINFO block.
This patch also makes sure we do not mark the 'fsinfo_inode' inode as dirty if
we are not FAT32 (FAT16 and FAT12 do not have the FSINFO block) or if we are in
R/O mode.
As a bonus, we can also remove the '->sync_fs()' and '->write_super()' FAT
call-back function because they become unneeded.
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@xxxxxxxxxxxxxxx>
---
fs/fat/fatent.c | 7 ++++++-
fs/fat/inode.c | 42 ++++++++++++------------------------------
2 files changed, 18 insertions(+), 31 deletions(-)
diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
index 85a1ec4..efa1000 100644
--- a/fs/fat/fatent.c
+++ b/fs/fat/fatent.c
@@ -310,7 +310,12 @@ void fat_ent_access_init(struct super_block *sb)
static void mark_fsinfo_dirty(struct super_block *sb)
{
- sb->s_dirt = 1;
+ struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+ if (sb->s_flags & MS_RDONLY || sbi->fat_bits != 32)
+ return;
+
+ __mark_inode_dirty(sbi->fsinfo_inode, I_DIRTY_SYNC);
}
static inline int fat_ent_update_ptr(struct super_block *sb,
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 91e9a8a..9a87ec4 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -459,37 +459,10 @@ static void fat_evict_inode(struct inode *inode)
fat_detach(inode);
}
-static void fat_write_super(struct super_block *sb)
-{
- lock_super(sb);
- sb->s_dirt = 0;
-
- if (!(sb->s_flags & MS_RDONLY))
- fat_clusters_flush(sb);
- unlock_super(sb);
-}
-
-static int fat_sync_fs(struct super_block *sb, int wait)
-{
- int err = 0;
-
- if (sb->s_dirt) {
- lock_super(sb);
- sb->s_dirt = 0;
- err = fat_clusters_flush(sb);
- unlock_super(sb);
- }
-
- return err;
-}
-
static void fat_put_super(struct super_block *sb)
{
struct msdos_sb_info *sbi = MSDOS_SB(sb);
- if (sb->s_dirt)
- fat_write_super(sb);
-
iput(sbi->fsinfo_inode);
iput(sbi->fat_inode);
@@ -662,7 +635,18 @@ retry:
static int fat_write_inode(struct inode *inode, struct writeback_control *wbc)
{
- return __fat_write_inode(inode, wbc->sync_mode == WB_SYNC_ALL);
+ int err;
+
+ if (inode->i_ino == MSDOS_FSINFO_INO) {
+ struct super_block *sb = inode->i_sb;
+
+ lock_super(sb);
+ err = fat_clusters_flush(sb);
+ unlock_super(sb);
+ } else
+ err = __fat_write_inode(inode, wbc->sync_mode == WB_SYNC_ALL);
+
+ return err;
}
int fat_sync_inode(struct inode *inode)
@@ -679,8 +663,6 @@ static const struct super_operations fat_sops = {
.write_inode = fat_write_inode,
.evict_inode = fat_evict_inode,
.put_super = fat_put_super,
- .write_super = fat_write_super,
- .sync_fs = fat_sync_fs,
.statfs = fat_statfs,
.remount_fs = fat_remount,
--
1.7.7.6
--
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