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![Zhang, Yanmin](/assets/img/avatar_default.png)
I run many ffsb test cases on JBODs (typically 13/12 disks). Comparing with kernel 2.6.30, 2.6.31-rc1 has about 16% regression with ffsb_create_4k. The sub test case creates files continuously for 10 minitues and every file is 1MB. Bisect located below patch.5cee5815d1
is first bad commit commit5cee5815d1
Author: Jan Kara <jack@suse.cz> Date: Mon Apr 27 16:43:51 2009 +0200 vfs: Make sys_sync() use fsync_super() (version 4) It is unnecessarily fragile to have two places (fsync_super() and do_sync()) doing data integrity sync of the filesystem. Alter __fsync_super() to accommodate needs of both callers and use it. So after this patch __fsync_super() is the only place where we gather all the calls needed to properly send all data on a filesystem to disk. As a matter of fact, ffsb calls sys_sync in the end to make sure all data is flushed to disks and the flushing is counted into the result. vmstat shows ffsb is blocked when syncing for a long time. With 2.6.30, ffsb is blocked for a short time. I checked the patch and did experiments to recover the original methods. Eventually, the root cause is the patch deletes the calling to wakeup_pdflush when syncing, so only ffsb is blocked on disk I/O. wakeup_pdflush could ask pdflush to write back pages with ffsb at the same time. [akpm@linux-foundation.org: restore comment too] Signed-off-by: Zhang Yanmin <yanmin_zhang@linux.intel.com> Cc: Jan Kara <jack@suse.cz> Cc: Al Viro <viro@zeniv.linux.org.uk> Acked-by: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
429 lines
11 KiB
C
429 lines
11 KiB
C
/*
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* High-level sync()-related operations
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*/
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#include <linux/kernel.h>
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#include <linux/file.h>
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#include <linux/fs.h>
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/writeback.h>
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#include <linux/syscalls.h>
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#include <linux/linkage.h>
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#include <linux/pagemap.h>
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#include <linux/quotaops.h>
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#include <linux/buffer_head.h>
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#include "internal.h"
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#define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
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SYNC_FILE_RANGE_WAIT_AFTER)
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/*
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* Do the filesystem syncing work. For simple filesystems sync_inodes_sb(sb, 0)
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* just dirties buffers with inodes so we have to submit IO for these buffers
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* via __sync_blockdev(). This also speeds up the wait == 1 case since in that
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* case write_inode() functions do sync_dirty_buffer() and thus effectively
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* write one block at a time.
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*/
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static int __sync_filesystem(struct super_block *sb, int wait)
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{
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/* Avoid doing twice syncing and cache pruning for quota sync */
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if (!wait)
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writeout_quota_sb(sb, -1);
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else
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sync_quota_sb(sb, -1);
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sync_inodes_sb(sb, wait);
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if (sb->s_op->sync_fs)
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sb->s_op->sync_fs(sb, wait);
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return __sync_blockdev(sb->s_bdev, wait);
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}
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/*
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* Write out and wait upon all dirty data associated with this
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* superblock. Filesystem data as well as the underlying block
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* device. Takes the superblock lock.
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*/
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int sync_filesystem(struct super_block *sb)
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{
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int ret;
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/*
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* We need to be protected against the filesystem going from
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* r/o to r/w or vice versa.
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*/
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WARN_ON(!rwsem_is_locked(&sb->s_umount));
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/*
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* No point in syncing out anything if the filesystem is read-only.
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*/
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if (sb->s_flags & MS_RDONLY)
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return 0;
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ret = __sync_filesystem(sb, 0);
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if (ret < 0)
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return ret;
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return __sync_filesystem(sb, 1);
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}
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EXPORT_SYMBOL_GPL(sync_filesystem);
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/*
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* Sync all the data for all the filesystems (called by sys_sync() and
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* emergency sync)
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*
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* This operation is careful to avoid the livelock which could easily happen
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* if two or more filesystems are being continuously dirtied. s_need_sync
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* is used only here. We set it against all filesystems and then clear it as
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* we sync them. So redirtied filesystems are skipped.
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*
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* But if process A is currently running sync_filesystems and then process B
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* calls sync_filesystems as well, process B will set all the s_need_sync
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* flags again, which will cause process A to resync everything. Fix that with
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* a local mutex.
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*/
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static void sync_filesystems(int wait)
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{
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struct super_block *sb;
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static DEFINE_MUTEX(mutex);
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mutex_lock(&mutex); /* Could be down_interruptible */
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spin_lock(&sb_lock);
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list_for_each_entry(sb, &super_blocks, s_list)
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sb->s_need_sync = 1;
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restart:
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list_for_each_entry(sb, &super_blocks, s_list) {
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if (!sb->s_need_sync)
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continue;
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sb->s_need_sync = 0;
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sb->s_count++;
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spin_unlock(&sb_lock);
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down_read(&sb->s_umount);
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if (!(sb->s_flags & MS_RDONLY) && sb->s_root)
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__sync_filesystem(sb, wait);
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up_read(&sb->s_umount);
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/* restart only when sb is no longer on the list */
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spin_lock(&sb_lock);
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if (__put_super_and_need_restart(sb))
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goto restart;
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}
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spin_unlock(&sb_lock);
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mutex_unlock(&mutex);
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}
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/*
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* sync everything. Start out by waking pdflush, because that writes back
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* all queues in parallel.
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*/
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SYSCALL_DEFINE0(sync)
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{
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wakeup_pdflush(0);
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sync_filesystems(0);
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sync_filesystems(1);
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if (unlikely(laptop_mode))
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laptop_sync_completion();
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return 0;
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}
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static void do_sync_work(struct work_struct *work)
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{
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/*
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* Sync twice to reduce the possibility we skipped some inodes / pages
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* because they were temporarily locked
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*/
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sync_filesystems(0);
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sync_filesystems(0);
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printk("Emergency Sync complete\n");
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kfree(work);
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}
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void emergency_sync(void)
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{
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struct work_struct *work;
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work = kmalloc(sizeof(*work), GFP_ATOMIC);
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if (work) {
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INIT_WORK(work, do_sync_work);
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schedule_work(work);
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}
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}
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/*
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* Generic function to fsync a file.
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*
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* filp may be NULL if called via the msync of a vma.
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*/
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int file_fsync(struct file *filp, struct dentry *dentry, int datasync)
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{
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struct inode * inode = dentry->d_inode;
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struct super_block * sb;
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int ret, err;
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/* sync the inode to buffers */
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ret = write_inode_now(inode, 0);
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/* sync the superblock to buffers */
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sb = inode->i_sb;
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if (sb->s_dirt && sb->s_op->write_super)
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sb->s_op->write_super(sb);
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/* .. finally sync the buffers to disk */
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err = sync_blockdev(sb->s_bdev);
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if (!ret)
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ret = err;
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return ret;
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}
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/**
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* vfs_fsync - perform a fsync or fdatasync on a file
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* @file: file to sync
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* @dentry: dentry of @file
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* @data: only perform a fdatasync operation
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*
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* Write back data and metadata for @file to disk. If @datasync is
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* set only metadata needed to access modified file data is written.
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*
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* In case this function is called from nfsd @file may be %NULL and
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* only @dentry is set. This can only happen when the filesystem
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* implements the export_operations API.
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*/
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int vfs_fsync(struct file *file, struct dentry *dentry, int datasync)
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{
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const struct file_operations *fop;
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struct address_space *mapping;
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int err, ret;
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/*
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* Get mapping and operations from the file in case we have
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* as file, or get the default values for them in case we
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* don't have a struct file available. Damn nfsd..
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*/
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if (file) {
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mapping = file->f_mapping;
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fop = file->f_op;
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} else {
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mapping = dentry->d_inode->i_mapping;
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fop = dentry->d_inode->i_fop;
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}
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if (!fop || !fop->fsync) {
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ret = -EINVAL;
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goto out;
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}
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ret = filemap_fdatawrite(mapping);
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/*
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* We need to protect against concurrent writers, which could cause
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* livelocks in fsync_buffers_list().
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*/
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mutex_lock(&mapping->host->i_mutex);
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err = fop->fsync(file, dentry, datasync);
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if (!ret)
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ret = err;
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mutex_unlock(&mapping->host->i_mutex);
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err = filemap_fdatawait(mapping);
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if (!ret)
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ret = err;
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out:
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return ret;
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}
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EXPORT_SYMBOL(vfs_fsync);
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static int do_fsync(unsigned int fd, int datasync)
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{
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struct file *file;
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int ret = -EBADF;
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file = fget(fd);
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if (file) {
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ret = vfs_fsync(file, file->f_path.dentry, datasync);
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fput(file);
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}
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return ret;
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}
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SYSCALL_DEFINE1(fsync, unsigned int, fd)
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{
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return do_fsync(fd, 0);
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}
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SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
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{
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return do_fsync(fd, 1);
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}
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/*
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* sys_sync_file_range() permits finely controlled syncing over a segment of
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* a file in the range offset .. (offset+nbytes-1) inclusive. If nbytes is
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* zero then sys_sync_file_range() will operate from offset out to EOF.
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*
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* The flag bits are:
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*
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* SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
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* before performing the write.
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*
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* SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
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* range which are not presently under writeback. Note that this may block for
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* significant periods due to exhaustion of disk request structures.
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*
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* SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
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* after performing the write.
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*
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* Useful combinations of the flag bits are:
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*
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* SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
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* in the range which were dirty on entry to sys_sync_file_range() are placed
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* under writeout. This is a start-write-for-data-integrity operation.
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*
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* SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
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* are not presently under writeout. This is an asynchronous flush-to-disk
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* operation. Not suitable for data integrity operations.
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*
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* SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
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* completion of writeout of all pages in the range. This will be used after an
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* earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
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* for that operation to complete and to return the result.
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*
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* SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
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* a traditional sync() operation. This is a write-for-data-integrity operation
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* which will ensure that all pages in the range which were dirty on entry to
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* sys_sync_file_range() are committed to disk.
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*
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*
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* SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
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* I/O errors or ENOSPC conditions and will return those to the caller, after
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* clearing the EIO and ENOSPC flags in the address_space.
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*
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* It should be noted that none of these operations write out the file's
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* metadata. So unless the application is strictly performing overwrites of
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* already-instantiated disk blocks, there are no guarantees here that the data
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* will be available after a crash.
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*/
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SYSCALL_DEFINE(sync_file_range)(int fd, loff_t offset, loff_t nbytes,
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unsigned int flags)
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{
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int ret;
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struct file *file;
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loff_t endbyte; /* inclusive */
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int fput_needed;
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umode_t i_mode;
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ret = -EINVAL;
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if (flags & ~VALID_FLAGS)
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goto out;
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endbyte = offset + nbytes;
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if ((s64)offset < 0)
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goto out;
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if ((s64)endbyte < 0)
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goto out;
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if (endbyte < offset)
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goto out;
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if (sizeof(pgoff_t) == 4) {
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if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
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/*
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* The range starts outside a 32 bit machine's
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* pagecache addressing capabilities. Let it "succeed"
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*/
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ret = 0;
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goto out;
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}
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if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
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/*
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* Out to EOF
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*/
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nbytes = 0;
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}
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}
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if (nbytes == 0)
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endbyte = LLONG_MAX;
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else
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endbyte--; /* inclusive */
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ret = -EBADF;
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file = fget_light(fd, &fput_needed);
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if (!file)
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goto out;
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i_mode = file->f_path.dentry->d_inode->i_mode;
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ret = -ESPIPE;
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if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
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!S_ISLNK(i_mode))
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goto out_put;
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ret = do_sync_mapping_range(file->f_mapping, offset, endbyte, flags);
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out_put:
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fput_light(file, fput_needed);
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out:
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return ret;
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}
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#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
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asmlinkage long SyS_sync_file_range(long fd, loff_t offset, loff_t nbytes,
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long flags)
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{
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return SYSC_sync_file_range((int) fd, offset, nbytes,
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(unsigned int) flags);
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}
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SYSCALL_ALIAS(sys_sync_file_range, SyS_sync_file_range);
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#endif
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/* It would be nice if people remember that not all the world's an i386
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when they introduce new system calls */
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SYSCALL_DEFINE(sync_file_range2)(int fd, unsigned int flags,
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loff_t offset, loff_t nbytes)
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{
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return sys_sync_file_range(fd, offset, nbytes, flags);
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}
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#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
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asmlinkage long SyS_sync_file_range2(long fd, long flags,
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loff_t offset, loff_t nbytes)
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{
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return SYSC_sync_file_range2((int) fd, (unsigned int) flags,
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offset, nbytes);
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}
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SYSCALL_ALIAS(sys_sync_file_range2, SyS_sync_file_range2);
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#endif
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/*
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* `endbyte' is inclusive
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*/
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int do_sync_mapping_range(struct address_space *mapping, loff_t offset,
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loff_t endbyte, unsigned int flags)
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{
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int ret;
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if (!mapping) {
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ret = -EINVAL;
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goto out;
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}
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ret = 0;
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if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
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ret = wait_on_page_writeback_range(mapping,
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offset >> PAGE_CACHE_SHIFT,
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endbyte >> PAGE_CACHE_SHIFT);
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if (ret < 0)
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goto out;
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}
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if (flags & SYNC_FILE_RANGE_WRITE) {
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ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
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WB_SYNC_ALL);
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if (ret < 0)
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goto out;
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}
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if (flags & SYNC_FILE_RANGE_WAIT_AFTER) {
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ret = wait_on_page_writeback_range(mapping,
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offset >> PAGE_CACHE_SHIFT,
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endbyte >> PAGE_CACHE_SHIFT);
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}
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out:
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return ret;
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}
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EXPORT_SYMBOL_GPL(do_sync_mapping_range);
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