Commit 1c0eeaf5 authored by Joern Engel's avatar Joern Engel Committed by Linus Torvalds

introduce I_SYNC

I_LOCK was used for several unrelated purposes, which caused deadlock
situations in certain filesystems as a side effect.  One of the purposes
now uses the new I_SYNC bit.

Also document the various bits and change their order from historical to
logical.

[bunk@stusta.de: make fs/inode.c:wake_up_inode() static]
Signed-off-by: default avatarJoern Engel <joern@wohnheim.fh-wedel.de>
Cc: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Cc: David Chinner <dgc@sgi.com>
Cc: Anton Altaparmakov <aia21@cam.ac.uk>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: default avatarAdrian Bunk <bunk@stusta.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2e6883bd
......@@ -100,11 +100,11 @@ void __mark_inode_dirty(struct inode *inode, int flags)
inode->i_state |= flags;
/*
* If the inode is locked, just update its dirty state.
* If the inode is being synced, just update its dirty state.
* The unlocker will place the inode on the appropriate
* superblock list, based upon its state.
*/
if (inode->i_state & I_LOCK)
if (inode->i_state & I_SYNC)
goto out;
/*
......@@ -172,6 +172,15 @@ static void requeue_io(struct inode *inode)
list_move(&inode->i_list, &inode->i_sb->s_more_io);
}
static void inode_sync_complete(struct inode *inode)
{
/*
* Prevent speculative execution through spin_unlock(&inode_lock);
*/
smp_mb();
wake_up_bit(&inode->i_state, __I_SYNC);
}
/*
* Move expired dirty inodes from @delaying_queue to @dispatch_queue.
*/
......@@ -225,11 +234,11 @@ __sync_single_inode(struct inode *inode, struct writeback_control *wbc)
int wait = wbc->sync_mode == WB_SYNC_ALL;
int ret;
BUG_ON(inode->i_state & I_LOCK);
BUG_ON(inode->i_state & I_SYNC);
/* Set I_LOCK, reset I_DIRTY */
/* Set I_SYNC, reset I_DIRTY */
dirty = inode->i_state & I_DIRTY;
inode->i_state |= I_LOCK;
inode->i_state |= I_SYNC;
inode->i_state &= ~I_DIRTY;
spin_unlock(&inode_lock);
......@@ -250,7 +259,7 @@ __sync_single_inode(struct inode *inode, struct writeback_control *wbc)
}
spin_lock(&inode_lock);
inode->i_state &= ~I_LOCK;
inode->i_state &= ~I_SYNC;
if (!(inode->i_state & I_FREEING)) {
if (!(inode->i_state & I_DIRTY) &&
mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
......@@ -305,7 +314,7 @@ __sync_single_inode(struct inode *inode, struct writeback_control *wbc)
list_move(&inode->i_list, &inode_unused);
}
}
wake_up_inode(inode);
inode_sync_complete(inode);
return ret;
}
......@@ -324,7 +333,7 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
else
WARN_ON(inode->i_state & I_WILL_FREE);
if ((wbc->sync_mode != WB_SYNC_ALL) && (inode->i_state & I_LOCK)) {
if ((wbc->sync_mode != WB_SYNC_ALL) && (inode->i_state & I_SYNC)) {
struct address_space *mapping = inode->i_mapping;
int ret;
......@@ -350,16 +359,16 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
/*
* It's a data-integrity sync. We must wait.
*/
if (inode->i_state & I_LOCK) {
DEFINE_WAIT_BIT(wq, &inode->i_state, __I_LOCK);
if (inode->i_state & I_SYNC) {
DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
wqh = bit_waitqueue(&inode->i_state, __I_LOCK);
wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
do {
spin_unlock(&inode_lock);
__wait_on_bit(wqh, &wq, inode_wait,
TASK_UNINTERRUPTIBLE);
spin_lock(&inode_lock);
} while (inode->i_state & I_LOCK);
} while (inode->i_state & I_SYNC);
}
return __sync_single_inode(inode, wbc);
}
......@@ -392,7 +401,7 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
* The inodes to be written are parked on sb->s_io. They are moved back onto
* sb->s_dirty as they are selected for writing. This way, none can be missed
* on the writer throttling path, and we get decent balancing between many
* throttled threads: we don't want them all piling up on __wait_on_inode.
* throttled threads: we don't want them all piling up on inode_sync_wait.
*/
static void
sync_sb_inodes(struct super_block *sb, struct writeback_control *wbc)
......@@ -661,7 +670,7 @@ int write_inode_now(struct inode *inode, int sync)
ret = __writeback_single_inode(inode, &wbc);
spin_unlock(&inode_lock);
if (sync)
wait_on_inode(inode);
inode_sync_wait(inode);
return ret;
}
EXPORT_SYMBOL(write_inode_now);
......@@ -736,7 +745,7 @@ int generic_osync_inode(struct inode *inode, struct address_space *mapping, int
err = err2;
}
else
wait_on_inode(inode);
inode_sync_wait(inode);
return err;
}
......
......@@ -384,7 +384,7 @@ static void hugetlbfs_forget_inode(struct inode *inode) __releases(inode_lock)
struct super_block *sb = inode->i_sb;
if (!hlist_unhashed(&inode->i_hash)) {
if (!(inode->i_state & (I_DIRTY|I_LOCK)))
if (!(inode->i_state & (I_DIRTY|I_SYNC)))
list_move(&inode->i_list, &inode_unused);
inodes_stat.nr_unused++;
if (!sb || (sb->s_flags & MS_ACTIVE)) {
......
......@@ -99,6 +99,15 @@ struct inodes_stat_t inodes_stat;
static struct kmem_cache * inode_cachep __read_mostly;
static void wake_up_inode(struct inode *inode)
{
/*
* Prevent speculative execution through spin_unlock(&inode_lock);
*/
smp_mb();
wake_up_bit(&inode->i_state, __I_LOCK);
}
static struct inode *alloc_inode(struct super_block *sb)
{
static const struct address_space_operations empty_aops;
......@@ -232,7 +241,7 @@ void __iget(struct inode * inode)
return;
}
atomic_inc(&inode->i_count);
if (!(inode->i_state & (I_DIRTY|I_LOCK)))
if (!(inode->i_state & (I_DIRTY|I_SYNC)))
list_move(&inode->i_list, &inode_in_use);
inodes_stat.nr_unused--;
}
......@@ -253,7 +262,7 @@ void clear_inode(struct inode *inode)
BUG_ON(inode->i_data.nrpages);
BUG_ON(!(inode->i_state & I_FREEING));
BUG_ON(inode->i_state & I_CLEAR);
wait_on_inode(inode);
inode_sync_wait(inode);
DQUOT_DROP(inode);
if (inode->i_sb->s_op->clear_inode)
inode->i_sb->s_op->clear_inode(inode);
......@@ -1071,7 +1080,7 @@ static void generic_forget_inode(struct inode *inode)
struct super_block *sb = inode->i_sb;
if (!hlist_unhashed(&inode->i_hash)) {
if (!(inode->i_state & (I_DIRTY|I_LOCK)))
if (!(inode->i_state & (I_DIRTY|I_SYNC)))
list_move(&inode->i_list, &inode_unused);
inodes_stat.nr_unused++;
if (sb->s_flags & MS_ACTIVE) {
......@@ -1314,15 +1323,6 @@ static void __wait_on_freeing_inode(struct inode *inode)
spin_lock(&inode_lock);
}
void wake_up_inode(struct inode *inode)
{
/*
* Prevent speculative execution through spin_unlock(&inode_lock);
*/
smp_mb();
wake_up_bit(&inode->i_state, __I_LOCK);
}
/*
* We rarely want to lock two inodes that do not have a parent/child
* relationship (such as directory, child inode) simultaneously. The
......
......@@ -1289,7 +1289,14 @@ int txCommit(tid_t tid, /* transaction identifier */
* commit the transaction synchronously, so the last iput
* will be done by the calling thread (or later)
*/
if (tblk->u.ip->i_state & I_LOCK)
/*
* I believe this code is no longer needed. Splitting I_LOCK
* into two bits, I_LOCK and I_SYNC should prevent this
* deadlock as well. But since I don't have a JFS testload
* to verify this, only a trivial s/I_LOCK/I_SYNC/ was done.
* Joern
*/
if (tblk->u.ip->i_state & I_SYNC)
tblk->xflag &= ~COMMIT_LAZY;
}
......
......@@ -133,7 +133,7 @@ xfs_ichgtime(
*/
SYNCHRONIZE();
ip->i_update_core = 1;
if (!(inode->i_state & I_LOCK))
if (!(inode->i_state & I_SYNC))
mark_inode_dirty_sync(inode);
}
......@@ -185,7 +185,7 @@ xfs_ichgtime_fast(
*/
SYNCHRONIZE();
ip->i_update_core = 1;
if (!(inode->i_state & I_LOCK))
if (!(inode->i_state & I_SYNC))
mark_inode_dirty_sync(inode);
}
......
......@@ -1261,16 +1261,68 @@ struct super_operations {
#endif
};
/* Inode state bits. Protected by inode_lock. */
#define I_DIRTY_SYNC 1 /* Not dirty enough for O_DATASYNC */
#define I_DIRTY_DATASYNC 2 /* Data-related inode changes pending */
#define I_DIRTY_PAGES 4 /* Data-related inode changes pending */
#define __I_LOCK 3
/*
* Inode state bits. Protected by inode_lock.
*
* Three bits determine the dirty state of the inode, I_DIRTY_SYNC,
* I_DIRTY_DATASYNC and I_DIRTY_PAGES.
*
* Four bits define the lifetime of an inode. Initially, inodes are I_NEW,
* until that flag is cleared. I_WILL_FREE, I_FREEING and I_CLEAR are set at
* various stages of removing an inode.
*
* Two bits are used for locking and completion notification, I_LOCK and I_SYNC.
*
* I_DIRTY_SYNC Inode itself is dirty.
* I_DIRTY_DATASYNC Data-related inode changes pending
* I_DIRTY_PAGES Inode has dirty pages. Inode itself may be clean.
* I_NEW get_new_inode() sets i_state to I_LOCK|I_NEW. Both
* are cleared by unlock_new_inode(), called from iget().
* I_WILL_FREE Must be set when calling write_inode_now() if i_count
* is zero. I_FREEING must be set when I_WILL_FREE is
* cleared.
* I_FREEING Set when inode is about to be freed but still has dirty
* pages or buffers attached or the inode itself is still
* dirty.
* I_CLEAR Set by clear_inode(). In this state the inode is clean
* and can be destroyed.
*
* Inodes that are I_WILL_FREE, I_FREEING or I_CLEAR are
* prohibited for many purposes. iget() must wait for
* the inode to be completely released, then create it
* anew. Other functions will just ignore such inodes,
* if appropriate. I_LOCK is used for waiting.
*
* I_LOCK Serves as both a mutex and completion notification.
* New inodes set I_LOCK. If two processes both create
* the same inode, one of them will release its inode and
* wait for I_LOCK to be released before returning.
* Inodes in I_WILL_FREE, I_FREEING or I_CLEAR state can
* also cause waiting on I_LOCK, without I_LOCK actually
* being set. find_inode() uses this to prevent returning
* nearly-dead inodes.
* I_SYNC Similar to I_LOCK, but limited in scope to writeback
* of inode dirty data. Having a seperate lock for this
* purpose reduces latency and prevents some filesystem-
* specific deadlocks.
*
* Q: Why does I_DIRTY_DATASYNC exist? It appears as if it could be replaced
* by (I_DIRTY_SYNC|I_DIRTY_PAGES).
* Q: What is the difference between I_WILL_FREE and I_FREEING?
* Q: igrab() only checks on (I_FREEING|I_WILL_FREE). Should it also check on
* I_CLEAR? If not, why?
*/
#define I_DIRTY_SYNC 1
#define I_DIRTY_DATASYNC 2
#define I_DIRTY_PAGES 4
#define I_NEW 8
#define I_WILL_FREE 16
#define I_FREEING 32
#define I_CLEAR 64
#define __I_LOCK 7
#define I_LOCK (1 << __I_LOCK)
#define I_FREEING 16
#define I_CLEAR 32
#define I_NEW 64
#define I_WILL_FREE 128
#define __I_SYNC 8
#define I_SYNC (1 << __I_SYNC)
#define I_DIRTY (I_DIRTY_SYNC | I_DIRTY_DATASYNC | I_DIRTY_PAGES)
......
......@@ -69,7 +69,6 @@ struct writeback_control {
* fs/fs-writeback.c
*/
void writeback_inodes(struct writeback_control *wbc);
void wake_up_inode(struct inode *inode);
int inode_wait(void *);
void sync_inodes_sb(struct super_block *, int wait);
void sync_inodes(int wait);
......@@ -81,6 +80,13 @@ static inline void wait_on_inode(struct inode *inode)
wait_on_bit(&inode->i_state, __I_LOCK, inode_wait,
TASK_UNINTERRUPTIBLE);
}
static inline void inode_sync_wait(struct inode *inode)
{
might_sleep();
wait_on_bit(&inode->i_state, __I_SYNC, inode_wait,
TASK_UNINTERRUPTIBLE);
}
/*
* mm/page-writeback.c
......
......@@ -37,7 +37,7 @@
/*
* The maximum number of pages to writeout in a single bdflush/kupdate
* operation. We do this so we don't hold I_LOCK against an inode for
* operation. We do this so we don't hold I_SYNC against an inode for
* enormous amounts of time, which would block a userspace task which has
* been forced to throttle against that inode. Also, the code reevaluates
* the dirty each time it has written this many pages.
......
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