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CacheFiles: Handle truncate unlocking the page we're reading

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Handle truncate unlocking the page we're attempting to read from the backing
device before the read has completed.

This was causing reports like the following to occur:

	Pid: 4765, comm: kslowd Not tainted 2.6.30.1 #1
	Call Trace:
	 [<ffffffffa0331d7a>] ? cachefiles_read_waiter+0xd9/0x147 [cachefiles]
	 [<ffffffff804b74bd>] ? __wait_on_bit+0x60/0x6f
	 [<ffffffff8022bbbb>] ? __wake_up_common+0x3f/0x71
	 [<ffffffff8022cc32>] ? __wake_up+0x30/0x44
	 [<ffffffff8024a41f>] ? __wake_up_bit+0x28/0x2d
	 [<ffffffffa003a793>] ? ext3_truncate+0x4d7/0x8ed [ext3]
	 [<ffffffff80281f90>] ? pagevec_lookup+0x17/0x1f
	 [<ffffffff8028c2ff>] ? unmap_mapping_range+0x59/0x1ff
	 [<ffffffff8022cc32>] ? __wake_up+0x30/0x44
	 [<ffffffff8028e286>] ? vmtruncate+0xc2/0xe2
	 [<ffffffff802b82cf>] ? inode_setattr+0x22/0x10a
	 [<ffffffffa003baa5>] ? ext3_setattr+0x17b/0x1e6 [ext3]
	 [<ffffffff802b853d>] ? notify_change+0x186/0x2c9
	 [<ffffffffa032d9de>] ? cachefiles_attr_changed+0x133/0x1cd [cachefiles]
	 [<ffffffffa032df7f>] ? cachefiles_lookup_object+0xcf/0x12a [cachefiles]
	 [<ffffffffa0318165>] ? fscache_lookup_object+0x110/0x122 [fscache]
	 [<ffffffffa03188c3>] ? fscache_object_slow_work_execute+0x590/0x6bc
	[fscache]
	 [<ffffffff80278f82>] ? slow_work_thread+0x285/0x43a
	 [<ffffffff8024a446>] ? autoremove_wake_function+0x0/0x2e
	 [<ffffffff80278cfd>] ? slow_work_thread+0x0/0x43a
	 [<ffffffff8024a317>] ? kthread+0x54/0x81
	 [<ffffffff8020c93a>] ? child_rip+0xa/0x20
	 [<ffffffff8024a2c3>] ? kthread+0x0/0x81
	 [<ffffffff8020c930>] ? child_rip+0x0/0x20
	CacheFiles: I/O Error: Readpage failed on backing file 200000000000810
	FS-Cache: Cache cachefiles stopped due to I/O error

Reported-by: Christian Kujau <lists@nerdbynature.de>
Reported-by: Takashi Iwai <tiwai@suse.de>
Reported-by: Duc Le Minh <duclm.vn@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells 2009-11-19 18:11:55 +00:00
parent a17754fb8c
commit 5e929b33c3
1 changed files with 93 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

99
fs/cachefiles/rdwr.c
View File

@ -40,8 +40,10 @@ static int cachefiles_read_waiter(wait_queue_t *wait, unsigned mode,
_debug("--- monitor %p %lx ---", page, page->flags);
if (!PageUptodate(page) && !PageError(page))
dump_stack();
if (!PageUptodate(page) && !PageError(page)) {
/* unlocked, not uptodate and not erronous? */
_debug("page probably truncated");
}
/* remove from the waitqueue */
list_del(&wait->task_list);
@ -60,6 +62,84 @@ static int cachefiles_read_waiter(wait_queue_t *wait, unsigned mode,
return 0;
}
/*
* handle a probably truncated page
* - check to see if the page is still relevant and reissue the read if
* possible
* - return -EIO on error, -ENODATA if the page is gone, -EINPROGRESS if we
* must wait again and 0 if successful
*/
static int cachefiles_read_reissue(struct cachefiles_object *object,
struct cachefiles_one_read *monitor)
{
struct address_space *bmapping = object->backer->d_inode->i_mapping;
struct page *backpage = monitor->back_page, *backpage2;
int ret;
kenter("{ino=%lx},{%lx,%lx}",
object->backer->d_inode->i_ino,
backpage->index, backpage->flags);
/* skip if the page was truncated away completely */
if (backpage->mapping != bmapping) {
kleave(" = -ENODATA [mapping]");
return -ENODATA;
}
backpage2 = find_get_page(bmapping, backpage->index);
if (!backpage2) {
kleave(" = -ENODATA [gone]");
return -ENODATA;
}
if (backpage != backpage2) {
put_page(backpage2);
kleave(" = -ENODATA [different]");
return -ENODATA;
}
/* the page is still there and we already have a ref on it, so we don't
* need a second */
put_page(backpage2);
INIT_LIST_HEAD(&monitor->op_link);
add_page_wait_queue(backpage, &monitor->monitor);
if (trylock_page(backpage)) {
ret = -EIO;
if (PageError(backpage))
goto unlock_discard;
ret = 0;
if (PageUptodate(backpage))
goto unlock_discard;
kdebug("reissue read");
ret = bmapping->a_ops->readpage(NULL, backpage);
if (ret < 0)
goto unlock_discard;
}
/* but the page may have been read before the monitor was installed, so
* the monitor may miss the event - so we have to ensure that we do get
* one in such a case */
if (trylock_page(backpage)) {
_debug("jumpstart %p {%lx}", backpage, backpage->flags);
unlock_page(backpage);
}
/* it'll reappear on the todo list */
kleave(" = -EINPROGRESS");
return -EINPROGRESS;
unlock_discard:
unlock_page(backpage);
spin_lock_irq(&object->work_lock);
list_del(&monitor->op_link);
spin_unlock_irq(&object->work_lock);
kleave(" = %d", ret);
return ret;
}
/*
* copy data from backing pages to netfs pages to complete a read operation
* - driven by FS-Cache's thread pool
@ -92,20 +172,26 @@ static void cachefiles_read_copier(struct fscache_operation *_op)
_debug("- copy {%lu}", monitor->back_page->index);
error = -EIO;
recheck:
if (PageUptodate(monitor->back_page)) {
copy_highpage(monitor->netfs_page, monitor->back_page);
pagevec_add(&pagevec, monitor->netfs_page);
fscache_mark_pages_cached(monitor->op, &pagevec);
error = 0;
}
if (error)
} else if (!PageError(monitor->back_page)) {
/* the page has probably been truncated */
error = cachefiles_read_reissue(object, monitor);
if (error == -EINPROGRESS)
goto next;
goto recheck;
} else {
cachefiles_io_error_obj(
object,
"Readpage failed on backing file %lx",
(unsigned long) monitor->back_page->flags);
error = -EIO;
}
page_cache_release(monitor->back_page);
@ -114,6 +200,7 @@ static void cachefiles_read_copier(struct fscache_operation *_op)
fscache_put_retrieval(op);
kfree(monitor);
next:
/* let the thread pool have some air occasionally */
max--;
if (max < 0 || need_resched()) {