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Diffstat (limited to 'fs/fs-writeback.c')
| -rw-r--r-- | fs/fs-writeback.c | 695 |
1 files changed, 695 insertions, 0 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c new file mode 100644 index 000000000000..d6efb36cab2a --- /dev/null +++ b/fs/fs-writeback.c @@ -0,0 +1,695 @@ +/* + * fs/fs-writeback.c + * + * Copyright (C) 2002, Linus Torvalds. + * + * Contains all the functions related to writing back and waiting + * upon dirty inodes against superblocks, and writing back dirty + * pages against inodes. ie: data writeback. Writeout of the + * inode itself is not handled here. + * + * 10Apr2002 akpm@zip.com.au + * Split out of fs/inode.c + * Additions for address_space-based writeback + */ + +#include <linux/kernel.h> +#include <linux/spinlock.h> +#include <linux/sched.h> +#include <linux/fs.h> +#include <linux/mm.h> +#include <linux/writeback.h> +#include <linux/blkdev.h> +#include <linux/backing-dev.h> +#include <linux/buffer_head.h> + +extern struct super_block *blockdev_superblock; + +/** + * __mark_inode_dirty - internal function + * @inode: inode to mark + * @flags: what kind of dirty (i.e. I_DIRTY_SYNC) + * Mark an inode as dirty. Callers should use mark_inode_dirty or + * mark_inode_dirty_sync. + * + * Put the inode on the super block's dirty list. + * + * CAREFUL! We mark it dirty unconditionally, but move it onto the + * dirty list only if it is hashed or if it refers to a blockdev. + * If it was not hashed, it will never be added to the dirty list + * even if it is later hashed, as it will have been marked dirty already. + * + * In short, make sure you hash any inodes _before_ you start marking + * them dirty. + * + * This function *must* be atomic for the I_DIRTY_PAGES case - + * set_page_dirty() is called under spinlock in several places. + * + * Note that for blockdevs, inode->dirtied_when represents the dirtying time of + * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of + * the kernel-internal blockdev inode represents the dirtying time of the + * blockdev's pages. This is why for I_DIRTY_PAGES we always use + * page->mapping->host, so the page-dirtying time is recorded in the internal + * blockdev inode. + */ +void __mark_inode_dirty(struct inode *inode, int flags) +{ + struct super_block *sb = inode->i_sb; + + /* + * Don't do this for I_DIRTY_PAGES - that doesn't actually + * dirty the inode itself + */ + if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) { + if (sb->s_op->dirty_inode) + sb->s_op->dirty_inode(inode); + } + + /* + * make sure that changes are seen by all cpus before we test i_state + * -- mikulas + */ + smp_mb(); + + /* avoid the locking if we can */ + if ((inode->i_state & flags) == flags) + return; + + if (unlikely(block_dump)) { + struct dentry *dentry = NULL; + const char *name = "?"; + + if (!list_empty(&inode->i_dentry)) { + dentry = list_entry(inode->i_dentry.next, + struct dentry, d_alias); + if (dentry && dentry->d_name.name) + name = (const char *) dentry->d_name.name; + } + + if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) + printk(KERN_DEBUG + "%s(%d): dirtied inode %lu (%s) on %s\n", + current->comm, current->pid, inode->i_ino, + name, inode->i_sb->s_id); + } + + spin_lock(&inode_lock); + if ((inode->i_state & flags) != flags) { + const int was_dirty = inode->i_state & I_DIRTY; + + inode->i_state |= flags; + + /* + * If the inode is locked, 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) + goto out; + + /* + * Only add valid (hashed) inodes to the superblock's + * dirty list. Add blockdev inodes as well. + */ + if (!S_ISBLK(inode->i_mode)) { + if (hlist_unhashed(&inode->i_hash)) + goto out; + } + if (inode->i_state & (I_FREEING|I_CLEAR)) + goto out; + + /* + * If the inode was already on s_dirty or s_io, don't + * reposition it (that would break s_dirty time-ordering). + */ + if (!was_dirty) { + inode->dirtied_when = jiffies; + list_move(&inode->i_list, &sb->s_dirty); + } + } +out: + spin_unlock(&inode_lock); +} + +EXPORT_SYMBOL(__mark_inode_dirty); + +static int write_inode(struct inode *inode, int sync) +{ + if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) + return inode->i_sb->s_op->write_inode(inode, sync); + return 0; +} + +/* + * Write a single inode's dirty pages and inode data out to disk. + * If `wait' is set, wait on the writeout. + * + * The whole writeout design is quite complex and fragile. We want to avoid + * starvation of particular inodes when others are being redirtied, prevent + * livelocks, etc. + * + * Called under inode_lock. + */ +static int +__sync_single_inode(struct inode *inode, struct writeback_control *wbc) +{ + unsigned dirty; + struct address_space *mapping = inode->i_mapping; + struct super_block *sb = inode->i_sb; + int wait = wbc->sync_mode == WB_SYNC_ALL; + int ret; + + BUG_ON(inode->i_state & I_LOCK); + + /* Set I_LOCK, reset I_DIRTY */ + dirty = inode->i_state & I_DIRTY; + inode->i_state |= I_LOCK; + inode->i_state &= ~I_DIRTY; + + spin_unlock(&inode_lock); + + ret = do_writepages(mapping, wbc); + + /* Don't write the inode if only I_DIRTY_PAGES was set */ + if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) { + int err = write_inode(inode, wait); + if (ret == 0) + ret = err; + } + + if (wait) { + int err = filemap_fdatawait(mapping); + if (ret == 0) + ret = err; + } + + spin_lock(&inode_lock); + inode->i_state &= ~I_LOCK; + if (!(inode->i_state & I_FREEING)) { + if (!(inode->i_state & I_DIRTY) && + mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) { + /* + * We didn't write back all the pages. nfs_writepages() + * sometimes bales out without doing anything. Redirty + * the inode. It is still on sb->s_io. + */ + if (wbc->for_kupdate) { + /* + * For the kupdate function we leave the inode + * at the head of sb_dirty so it will get more + * writeout as soon as the queue becomes + * uncongested. + */ + inode->i_state |= I_DIRTY_PAGES; + list_move_tail(&inode->i_list, &sb->s_dirty); + } else { + /* + * Otherwise fully redirty the inode so that + * other inodes on this superblock will get some + * writeout. Otherwise heavy writing to one + * file would indefinitely suspend writeout of + * all the other files. + */ + inode->i_state |= I_DIRTY_PAGES; + inode->dirtied_when = jiffies; + list_move(&inode->i_list, &sb->s_dirty); + } + } else if (inode->i_state & I_DIRTY) { + /* + * Someone redirtied the inode while were writing back + * the pages. + */ + list_move(&inode->i_list, &sb->s_dirty); + } else if (atomic_read(&inode->i_count)) { + /* + * The inode is clean, inuse + */ + list_move(&inode->i_list, &inode_in_use); + } else { + /* + * The inode is clean, unused + */ + list_move(&inode->i_list, &inode_unused); + inodes_stat.nr_unused++; + } + } + wake_up_inode(inode); + return ret; +} + +/* + * Write out an inode's dirty pages. Called under inode_lock. + */ +static int +__writeback_single_inode(struct inode *inode, + struct writeback_control *wbc) +{ + wait_queue_head_t *wqh; + + if ((wbc->sync_mode != WB_SYNC_ALL) && (inode->i_state & I_LOCK)) { + list_move(&inode->i_list, &inode->i_sb->s_dirty); + return 0; + } + + /* + * It's a data-integrity sync. We must wait. + */ + if (inode->i_state & I_LOCK) { + DEFINE_WAIT_BIT(wq, &inode->i_state, __I_LOCK); + + wqh = bit_waitqueue(&inode->i_state, __I_LOCK); + do { + __iget(inode); + spin_unlock(&inode_lock); + __wait_on_bit(wqh, &wq, inode_wait, + TASK_UNINTERRUPTIBLE); + iput(inode); + spin_lock(&inode_lock); + } while (inode->i_state & I_LOCK); + } + return __sync_single_inode(inode, wbc); +} + +/* + * Write out a superblock's list of dirty inodes. A wait will be performed + * upon no inodes, all inodes or the final one, depending upon sync_mode. + * + * If older_than_this is non-NULL, then only write out inodes which + * had their first dirtying at a time earlier than *older_than_this. + * + * If we're a pdlfush thread, then implement pdflush collision avoidance + * against the entire list. + * + * WB_SYNC_HOLD is a hack for sys_sync(): reattach the inode to sb->s_dirty so + * that it can be located for waiting on in __writeback_single_inode(). + * + * Called under inode_lock. + * + * If `bdi' is non-zero then we're being asked to writeback a specific queue. + * This function assumes that the blockdev superblock's inodes are backed by + * a variety of queues, so all inodes are searched. For other superblocks, + * assume that all inodes are backed by the same queue. + * + * FIXME: this linear search could get expensive with many fileystems. But + * how to fix? We need to go from an address_space to all inodes which share + * a queue with that address_space. (Easy: have a global "dirty superblocks" + * list). + * + * 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. + */ +static void +sync_sb_inodes(struct super_block *sb, struct writeback_control *wbc) +{ + const unsigned long start = jiffies; /* livelock avoidance */ + + if (!wbc->for_kupdate || list_empty(&sb->s_io)) + list_splice_init(&sb->s_dirty, &sb->s_io); + + while (!list_empty(&sb->s_io)) { + struct inode *inode = list_entry(sb->s_io.prev, + struct inode, i_list); + struct address_space *mapping = inode->i_mapping; + struct backing_dev_info *bdi = mapping->backing_dev_info; + long pages_skipped; + + if (!bdi_cap_writeback_dirty(bdi)) { + list_move(&inode->i_list, &sb->s_dirty); + if (sb == blockdev_superblock) { + /* + * Dirty memory-backed blockdev: the ramdisk + * driver does this. Skip just this inode + */ + continue; + } + /* + * Dirty memory-backed inode against a filesystem other + * than the kernel-internal bdev filesystem. Skip the + * entire superblock. + */ + break; + } + + if (wbc->nonblocking && bdi_write_congested(bdi)) { + wbc->encountered_congestion = 1; + if (sb != blockdev_superblock) + break; /* Skip a congested fs */ + list_move(&inode->i_list, &sb->s_dirty); + continue; /* Skip a congested blockdev */ + } + + if (wbc->bdi && bdi != wbc->bdi) { + if (sb != blockdev_superblock) + break; /* fs has the wrong queue */ + list_move(&inode->i_list, &sb->s_dirty); + continue; /* blockdev has wrong queue */ + } + + /* Was this inode dirtied after sync_sb_inodes was called? */ + if (time_after(inode->dirtied_when, start)) + break; + + /* Was this inode dirtied too recently? */ + if (wbc->older_than_this && time_after(inode->dirtied_when, + *wbc->older_than_this)) + break; + + /* Is another pdflush already flushing this queue? */ + if (current_is_pdflush() && !writeback_acquire(bdi)) + break; + + BUG_ON(inode->i_state & I_FREEING); + __iget(inode); + pages_skipped = wbc->pages_skipped; + __writeback_single_inode(inode, wbc); + if (wbc->sync_mode == WB_SYNC_HOLD) { + inode->dirtied_when = jiffies; + list_move(&inode->i_list, &sb->s_dirty); + } + if (current_is_pdflush()) + writeback_release(bdi); + if (wbc->pages_skipped != pages_skipped) { + /* + * writeback is not making progress due to locked + * buffers. Skip this inode for now. + */ + list_move(&inode->i_list, &sb->s_dirty); + } + spin_unlock(&inode_lock); + cond_resched(); + iput(inode); + spin_lock(&inode_lock); + if (wbc->nr_to_write <= 0) + break; + } + return; /* Leave any unwritten inodes on s_io */ +} + +/* + * Start writeback of dirty pagecache data against all unlocked inodes. + * + * Note: + * We don't need to grab a reference to superblock here. If it has non-empty + * ->s_dirty it's hadn't been killed yet and kill_super() won't proceed + * past sync_inodes_sb() until both the ->s_dirty and ->s_io lists are + * empty. Since __sync_single_inode() regains inode_lock before it finally moves + * inode from superblock lists we are OK. + * + * If `older_than_this' is non-zero then only flush inodes which have a + * flushtime older than *older_than_this. + * + * If `bdi' is non-zero then we will scan the first inode against each + * superblock until we find the matching ones. One group will be the dirty + * inodes against a filesystem. Then when we hit the dummy blockdev superblock, + * sync_sb_inodes will seekout the blockdev which matches `bdi'. Maybe not + * super-efficient but we're about to do a ton of I/O... + */ +void +writeback_inodes(struct writeback_control *wbc) +{ + struct super_block *sb; + + might_sleep(); + spin_lock(&sb_lock); +restart: + sb = sb_entry(super_blocks.prev); + for (; sb != sb_entry(&super_blocks); sb = sb_entry(sb->s_list.prev)) { + if (!list_empty(&sb->s_dirty) || !list_empty(&sb->s_io)) { + /* we're making our own get_super here */ + sb->s_count++; + spin_unlock(&sb_lock); + /* + * If we can't get the readlock, there's no sense in + * waiting around, most of the time the FS is going to + * be unmounted by the time it is released. + */ + if (down_read_trylock(&sb->s_umount)) { + if (sb->s_root) { + spin_lock(&inode_lock); + sync_sb_inodes(sb, wbc); + spin_unlock(&inode_lock); + } + up_read(&sb->s_umount); + } + spin_lock(&sb_lock); + if (__put_super_and_need_restart(sb)) + goto restart; + } + if (wbc->nr_to_write <= 0) + break; + } + spin_unlock(&sb_lock); +} + +/* + * writeback and wait upon the filesystem's dirty inodes. The caller will + * do this in two passes - one to write, and one to wait. WB_SYNC_HOLD is + * used to park the written inodes on sb->s_dirty for the wait pass. + * + * A finite limit is set on the number of pages which will be written. + * To prevent infinite livelock of sys_sync(). + * + * We add in the number of potentially dirty inodes, because each inode write + * can dirty pagecache in the underlying blockdev. + */ +void sync_inodes_sb(struct super_block *sb, int wait) +{ + struct writeback_control wbc = { + .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_HOLD, + }; + unsigned long nr_dirty = read_page_state(nr_dirty); + unsigned long nr_unstable = read_page_state(nr_unstable); + + wbc.nr_to_write = nr_dirty + nr_unstable + + (inodes_stat.nr_inodes - inodes_stat.nr_unused) + + nr_dirty + nr_unstable; + wbc.nr_to_write += wbc.nr_to_write / 2; /* Bit more for luck */ + spin_lock(&inode_lock); + sync_sb_inodes(sb, &wbc); + spin_unlock(&inode_lock); +} + +/* + * Rather lame livelock avoidance. + */ +static void set_sb_syncing(int val) +{ + struct super_block *sb; + spin_lock(&sb_lock); + sb = sb_entry(super_blocks.prev); + for (; sb != sb_entry(&super_blocks); sb = sb_entry(sb->s_list.prev)) { + sb->s_syncing = val; + } + spin_unlock(&sb_lock); +} + +/* + * Find a superblock with inodes that need to be synced + */ +static struct super_block *get_super_to_sync(void) +{ + struct super_block *sb; +restart: + spin_lock(&sb_lock); + sb = sb_entry(super_blocks.prev); + for (; sb != sb_entry(&super_blocks); sb = sb_entry(sb->s_list.prev)) { + if (sb->s_syncing) + continue; + sb->s_syncing = 1; + sb->s_count++; + spin_unlock(&sb_lock); + down_read(&sb->s_umount); + if (!sb->s_root) { + drop_super(sb); + goto restart; + } + return sb; + } + spin_unlock(&sb_lock); + return NULL; +} + +/** + * sync_inodes + * + * sync_inodes() goes through each super block's dirty inode list, writes the + * inodes out, waits on the writeout and puts the inodes back on the normal + * list. + * + * This is for sys_sync(). fsync_dev() uses the same algorithm. The subtle + * part of the sync functions is that the blockdev "superblock" is processed + * last. This is because the write_inode() function of a typical fs will + * perform no I/O, but will mark buffers in the blockdev mapping as dirty. + * What we want to do is to perform all that dirtying first, and then write + * back all those inode blocks via the blockdev mapping in one sweep. So the + * additional (somewhat redundant) sync_blockdev() calls here are to make + * sure that really happens. Because if we call sync_inodes_sb(wait=1) with + * outstanding dirty inodes, the writeback goes block-at-a-time within the + * filesystem's write_inode(). This is extremely slow. + */ +void sync_inodes(int wait) +{ + struct super_block *sb; + + set_sb_syncing(0); + while ((sb = get_super_to_sync()) != NULL) { + sync_inodes_sb(sb, 0); + sync_blockdev(sb->s_bdev); + drop_super(sb); + } + if (wait) { + set_sb_syncing(0); + while ((sb = get_super_to_sync()) != NULL) { + sync_inodes_sb(sb, 1); + sync_blockdev(sb->s_bdev); + drop_super(sb); + } + } +} + +/** + * write_inode_now - write an inode to disk + * @inode: inode to write to disk + * @sync: whether the write should be synchronous or not + * + * This function commits an inode to disk immediately if it is + * dirty. This is primarily needed by knfsd. + */ + +int write_inode_now(struct inode *inode, int sync) +{ + int ret; + struct writeback_control wbc = { + .nr_to_write = LONG_MAX, + .sync_mode = WB_SYNC_ALL, + }; + + if (!mapping_cap_writeback_dirty(inode->i_mapping)) + return 0; + + might_sleep(); + spin_lock(&inode_lock); + ret = __writeback_single_inode(inode, &wbc); + spin_unlock(&inode_lock); + if (sync) + wait_on_inode(inode); + return ret; +} +EXPORT_SYMBOL(write_inode_now); + +/** + * sync_inode - write an inode and its pages to disk. + * @inode: the inode to sync + * @wbc: controls the writeback mode + * + * sync_inode() will write an inode and its pages to disk. It will also + * correctly update the inode on its superblock's dirty inode lists and will + * update inode->i_state. + * + * The caller must have a ref on the inode. + */ +int sync_inode(struct inode *inode, struct writeback_control *wbc) +{ + int ret; + + spin_lock(&inode_lock); + ret = __writeback_single_inode(inode, wbc); + spin_unlock(&inode_lock); + return ret; +} +EXPORT_SYMBOL(sync_inode); + +/** + * generic_osync_inode - flush all dirty data for a given inode to disk + * @inode: inode to write + * @what: what to write and wait upon + * + * This can be called by file_write functions for files which have the + * O_SYNC flag set, to flush dirty writes to disk. + * + * @what is a bitmask, specifying which part of the inode's data should be + * written and waited upon: + * + * OSYNC_DATA: i_mapping's dirty data + * OSYNC_METADATA: the buffers at i_mapping->private_list + * OSYNC_INODE: the inode itself + */ + +int generic_osync_inode(struct inode *inode, struct address_space *mapping, int what) +{ + int err = 0; + int need_write_inode_now = 0; + int err2; + + current->flags |= PF_SYNCWRITE; + if (what & OSYNC_DATA) + err = filemap_fdatawrite(mapping); + if (what & (OSYNC_METADATA|OSYNC_DATA)) { + err2 = sync_mapping_buffers(mapping); + if (!err) + err = err2; + } + if (what & OSYNC_DATA) { + err2 = filemap_fdatawait(mapping); + if (!err) + err = err2; + } + current->flags &= ~PF_SYNCWRITE; + + spin_lock(&inode_lock); + if ((inode->i_state & I_DIRTY) && + ((what & OSYNC_INODE) || (inode->i_state & I_DIRTY_DATASYNC))) + need_write_inode_now = 1; + spin_unlock(&inode_lock); + + if (need_write_inode_now) { + err2 = write_inode_now(inode, 1); + if (!err) + err = err2; + } + else + wait_on_inode(inode); + + return err; +} + +EXPORT_SYMBOL(generic_osync_inode); + +/** + * writeback_acquire: attempt to get exclusive writeback access to a device + * @bdi: the device's backing_dev_info structure + * + * It is a waste of resources to have more than one pdflush thread blocked on + * a single request queue. Exclusion at the request_queue level is obtained + * via a flag in the request_queue's backing_dev_info.state. + * + * Non-request_queue-backed address_spaces will share default_backing_dev_info, + * unless they implement their own. Which is somewhat inefficient, as this + * may prevent concurrent writeback against multiple devices. + */ +int writeback_acquire(struct backing_dev_info *bdi) +{ + return !test_and_set_bit(BDI_pdflush, &bdi->state); +} + +/** + * writeback_in_progress: determine whether there is writeback in progress + * against a backing device. + * @bdi: the device's backing_dev_info structure. + */ +int writeback_in_progress(struct backing_dev_info *bdi) +{ + return test_bit(BDI_pdflush, &bdi->state); +} + +/** + * writeback_release: relinquish exclusive writeback access against a device. + * @bdi: the device's backing_dev_info structure + */ +void writeback_release(struct backing_dev_info *bdi) +{ + BUG_ON(!writeback_in_progress(bdi)); + clear_bit(BDI_pdflush, &bdi->state); +} |