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2014-01-28Btrfs: move the extent buffer radix tree into the fs_infoJosef Bacik1-5/+3
I need to create a fake tree to test qgroups and I don't want to have to setup a fake btree_inode. The fact is we only use the radix tree for the fs_info, so everybody else who allocates an extent_io_tree is just wasting the space anyway. This patch moves the radix tree and its lock into btrfs_fs_info so there is less stuff I have to fake to do qgroup sanity tests. Thanks, Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Chris Mason <clm@fb.com>
2014-01-28Btrfs: use a bit to track if we're in the radix treeJosef Bacik1-0/+1
For creating a dummy in-memory btree I need to be able to use the radix tree to keep track of the buffers like normal extent buffers. With dummy buffers we skip the radix tree step, and we still want to do that for the tree mod log dummy buffers but for my test buffers we need to be able to remove them from the radix tree like normal. This will give me a way to do that. Thanks, Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Chris Mason <clm@fb.com>
2013-11-11Btrfs: Simplify the logic in alloc_extent_buffer() for existing extent ↵Chandra Seetharaman1-1/+1
buffer case alloc_extent_buffer() uses radix_tree_lookup() when radix_tree_insert() fails with EEXIST. That part of the code is very similar to the code in find_extent_buffer(). This patch replaces radix_tree_lookup() and surrounding code in alloc_extent_buffer() with find_extent_buffer(). Note that radix_tree_lookup() does not need to be protected by tree->buffer_lock. It is protected by eb->refs. While at it, this patch - changes the other usage of radix_tree_lookup() in alloc_extent_buffer() with find_extent_buffer() to reduce redundancy. - removes the unused argument 'len' to find_extent_buffer(). Signed-Off-by: Chandra Seetharaman <sekharan@us.ibm.com> Reviewed-by: Zach Brown <zab@redhat.com> Signed-off-by: Josef Bacik <jbacik@fusionio.com> Signed-off-by: Chris Mason <chris.mason@fusionio.com>
2013-11-11Btrfs: add tests for find_lock_delalloc_rangeJosef Bacik1-0/+6
So both Liu and I made huge messes of find_lock_delalloc_range trying to fix stuff, me first by fixing extent size, then him by fixing something I broke and then me again telling him to fix it a different way. So this is obviously a candidate for some testing. This patch adds a pseudo fs so we can allocate fake inodes for tests that need an inode or pages. Then it addes a bunch of tests to make sure find_lock_delalloc_range is acting the way it is supposed to. With this patch and all of our previous patches to find_lock_delalloc_range I am sure it is working as expected now. Thanks, Signed-off-by: Josef Bacik <jbacik@fusionio.com> Signed-off-by: Chris Mason <chris.mason@fusionio.com>
2013-09-01btrfs: mark some local function as 'static'Sergei Trofimovich1-1/+0
Cc: Josef Bacik <jbacik@fusionio.com> Cc: Chris Mason <chris.mason@fusionio.com> Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org> Signed-off-by: Josef Bacik <jbacik@fusionio.com> Signed-off-by: Chris Mason <chris.mason@fusionio.com>
2013-09-01btrfs: Introduce extent_read_full_page_nolock()Mark Fasheh1-0/+3
We want this for btrfs_extent_same. Basically readpage and friends do their own extent locking but for the purposes of dedupe, we want to have both files locked down across a set of readpage operations (so that we can compare data). Introduce this variant and a flag which can be set for extent_read_full_page() to indicate that we are already locked. Partial credit for this patch goes to Gabriel de Perthuis <g2p.code@gmail.com> as I have included a fix from him to the original patch which avoids a deadlock on compressed extents. Signed-off-by: Mark Fasheh <mfasheh@suse.de> Signed-off-by: Josef Bacik <jbacik@fusionio.com> Signed-off-by: Chris Mason <chris.mason@fusionio.com>
2013-09-01Btrfs: cleanup arguments to extent_clear_unlock_delallocJosef Bacik1-12/+9
This patch removes the io_tree argument for extent_clear_unlock_delalloc since we always use &BTRFS_I(inode)->io_tree, and it separates out the extent tree operations from the page operations. This way we just pass in the extent bits we want to clear and then pass in the operations we want done to the pages. This is because I'm going to fix what extent bits we clear in some cases and rather than add a bunch of new flags we'll just use the actual extent bits we want to clear. Thanks, Signed-off-by: Josef Bacik <jbacik@fusionio.com> Signed-off-by: Chris Mason <chris.mason@fusionio.com>
2013-09-01Btrfs: don't cache the csum value into the extent state treeMiao Xie1-6/+4
Before applying this patch, we cached the csum value into the extent state tree when reading some data from the disk, this operation increased the lock contention of the state tree. Now, we just store the csum value into the bio structure or other unshared structure, so we can reduce the lock contention. Signed-off-by: Miao Xie <miaox@cn.fujitsu.com> Signed-off-by: Josef Bacik <jbacik@fusionio.com> Signed-off-by: Chris Mason <chris.mason@fusionio.com>
2013-07-02Btrfs: check if we can nocow if we don't have data spaceJosef Bacik1-0/+1
We always just try and reserve data space when we write, but if we are out of space but have prealloc'ed extents we should still successfully write. This patch will try and see if we can write to prealloc'ed space and if we can go ahead and allow the write to continue. With this patch we now pass xfstests generic/274. Thanks, Signed-off-by: Josef Bacik <jbacik@fusionio.com>
2013-05-17Btrfs: use a btrfs bioset instead of abusing bio internalsChris Mason1-0/+2
Btrfs has been pointer tagging bi_private and using bi_bdev to store the stripe index and mirror number of failed IOs. As bios bubble back up through the call chain, we use these to decide if and how to retry our IOs. They are also used to count IO failures on a per device basis. Recently a bio tracepoint was added lead to crashes because we were abusing bi_bdev. This commit adds a btrfs bioset, and creates explicit fields for the mirror number and stripe index. The plan is to extend this structure for all of the fields currently in struct btrfs_bio, which will mean one less kmalloc in our IO path. Signed-off-by: Chris Mason <chris.mason@fusionio.com> Reported-by: Tejun Heo <tj@kernel.org>
2013-05-06btrfs: use unsigned long type for extent state bitsDavid Sterba1-11/+12
Signed-off-by: David Sterba <dsterba@suse.cz> Signed-off-by: Josef Bacik <jbacik@fusionio.com>
2013-05-06btrfs: remove unused gfp mask parameter from release_extent_buffer callchainDavid Sterba1-1/+1
It's unused since 0b32f4bbb423f02ac. Signed-off-by: David Sterba <dsterba@suse.cz> Signed-off-by: Josef Bacik <jbacik@fusionio.com>
2013-05-06btrfs: make static code static & remove dead codeEric Sandeen1-8/+0
Big patch, but all it does is add statics to functions which are in fact static, then remove the associated dead-code fallout. removed functions: btrfs_iref_to_path() __btrfs_lookup_delayed_deletion_item() __btrfs_search_delayed_insertion_item() __btrfs_search_delayed_deletion_item() find_eb_for_page() btrfs_find_block_group() range_straddles_pages() extent_range_uptodate() btrfs_file_extent_length() btrfs_scrub_cancel_devid() btrfs_start_transaction_lflush() btrfs_print_tree() is left because it is used for debugging. btrfs_start_transaction_lflush() and btrfs_reada_detach() are left for symmetry. ulist.c functions are left, another patch will take care of those. Signed-off-by: Eric Sandeen <sandeen@redhat.com> Signed-off-by: Josef Bacik <jbacik@fusionio.com>
2013-05-06btrfs: move leak debug code to functionsEric Sandeen1-1/+5
Clean up the leak debugging in extent_io.c by moving the debug code into functions. This also removes the list_heads used for debugging from the extent_buffer and extent_state structures when debug is not enabled. Since we need a global debug config to do that last part, implement CONFIG_BTRFS_DEBUG to accommodate. Thanks to Dave Sterba for the Kconfig bit. Signed-off-by: Eric Sandeen <sandeen@redhat.com> Reviewed-by: David Sterba <dsterba@suse.cz> Signed-off-by: Josef Bacik <jbacik@fusionio.com>
2013-05-06Btrfs: cleanup destroy_marked_extentsJosef Bacik1-0/+1
We can just look up the extent_buffers for the range and free stuff that way. This makes the cleanup a bit cleaner and we can make sure to evict the extent_buffers pretty quickly by marking them as stale. Thanks, Signed-off-by: Josef Bacik <jbacik@fusionio.com>
2013-05-06Btrfs: improve the performance of the csums lookupMiao Xie1-0/+4
It is very likely that there are several blocks in bio, it is very inefficient if we get their csums one by one. This patch improves this problem by getting the csums in batch. According to the result of the following test, the execute time of __btrfs_lookup_bio_sums() is down by ~28%(300us -> 217us). # dd if=<mnt>/file of=/dev/null bs=1M count=1024 Signed-off-by: Miao Xie <miaox@cn.fujitsu.com> Signed-off-by: Josef Bacik <jbacik@fusionio.com>
2013-03-26Btrfs: fix race between mmap writes and compressionChris Mason1-0/+2
Btrfs uses page_mkwrite to ensure stable pages during crc calculations and mmap workloads. We call clear_page_dirty_for_io before we do any crcs, and this forces any application with the file mapped to wait for the crc to finish before it is allowed to change the file. With compression on, the clear_page_dirty_for_io step is happening after we've compressed the pages. This means the applications might be changing the pages while we are compressing them, and some of those modifications might not hit the disk. This commit adds the clear_page_dirty_for_io before compression starts and makes sure to redirty the page if we have to fallback to uncompressed IO as well. Signed-off-by: Chris Mason <chris.mason@fusionio.com> Reported-by: Alexandre Oliva <oliva@gnu.org> cc: stable@vger.kernel.org
2013-02-28btrfs: use only inline_pages from extent bufferDavid Sterba1-2/+1
The nodesize is capped at 64k and there are enough pages preallocated in extent_buffer::inline_pages. The fallback to kmalloc never happened because even on the smallest page size considered (4k) inline_pages covered the needs. Signed-off-by: David Sterba <dsterba@suse.cz> Signed-off-by: Josef Bacik <jbacik@fusionio.com>
2013-02-20Merge branch 'raid56-experimental' into for-linus-3.9Chris Mason1-1/+1
Signed-off-by: Chris Mason <chris.mason@fusionio.com> Conflicts: fs/btrfs/ctree.h fs/btrfs/extent-tree.c fs/btrfs/inode.c fs/btrfs/volumes.c
2013-02-20Btrfs: remove unused extent io tree ops V2Josef Bacik1-3/+0
Nobody uses these io tree ops anymore so just remove them and clean up the code a bit. Thanks, Signed-off-by: Josef Bacik <jbacik@fusionio.com>
2013-02-01Btrfs: add rw argument to merge_bio_hook()David Woodhouse1-1/+1
We'll want to merge writes so they can fill a full RAID[56] stripe, but not necessarily reads. Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> Signed-off-by: Chris Mason <chris.mason@fusionio.com>
2012-12-12Btrfs: pass fs_info to btrfs_map_block() instead of mapping_treeStefan Behrens1-2/+2
This is required for the device replace procedure in a later step. Two calling functions also had to be changed to have the fs_info pointer: repair_io_failure() and scrub_setup_recheck_block(). Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de> Signed-off-by: Chris Mason <chris.mason@fusionio.com>
2012-10-09btrfs: move inline function code to header fileRobin Dong1-2/+12
When building btrfs from kernel code, it will report: fs/btrfs/extent_io.h:281: warning: 'extent_buffer_page' declared inline after being called fs/btrfs/extent_io.h:281: warning: previous declaration of 'extent_buffer_page' was here fs/btrfs/extent_io.h:280: warning: 'num_extent_pages' declared inline after being called fs/btrfs/extent_io.h:280: warning: previous declaration of 'num_extent_pages' was here because of the wrong declaration of inline functions. Signed-off-by: Robin Dong <sanbai@taobao.com>
2012-10-09Btrfs: cache extent state when writing out dirty metadata pagesJosef Bacik1-2/+4
Everytime we write out dirty pages we search for an offset in the tree, convert the bits in the state, and then when we wait we search for the offset again and clear the bits. So for every dirty range in the io tree we are doing 4 rb searches, which is suboptimal. With this patch we are only doing 2 searches for every cycle (modulo weird things happening). Thanks, Signed-off-by: Josef Bacik <jbacik@fusionio.com>
2012-10-09Btrfs: do not async metadata csumming in certain situationsJosef Bacik1-0/+1
There are a coule scenarios where farming metadata csumming off to an async thread doesn't help. The first is if our processor supports crc32c, in which case the csumming will be fast and so the overhead of the async model is not worth the cost. The other case is for our tree log. We will be making that stuff dirty and writing it out and waiting for it immediately. Even with software crc32c this gives me a ~15% increase in speed with O_SYNC workloads. Thanks, Signed-off-by: Josef Bacik <jbacik@fusionio.com>
2012-10-01Btrfs: use flag EXTENT_DEFRAG for snapshot-aware defragLiu Bo1-0/+2
We're going to use this flag EXTENT_DEFRAG to indicate which range belongs to defragment so that we can implement snapshow-aware defrag: We set the EXTENT_DEFRAG flag when dirtying the extents that need defragmented, so later on writeback thread can differentiate between normal writeback and writeback started by defragmentation. Original-Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
2012-05-31Merge branch 'for-chris' of git://git.jan-o-sch.net/btrfs-unstable into ↵Chris Mason1-0/+3
for-linus Conflicts: fs/btrfs/ulist.h Signed-off-by: Chris Mason <chris.mason@oracle.com>
2012-05-30Btrfs: finish ordered extents in their own threadJosef Bacik1-3/+2
We noticed that the ordered extent completion doesn't really rely on having a page and that it could be done independantly of ending the writeback on a page. This patch makes us not do the threaded endio stuff for normal buffered writes and direct writes so we can end page writeback as soon as possible (in irq context) and only start threads to do the ordered work when it is actually done. Compression needs to be reworked some to take advantage of this as well, but atm it has to do a find_get_page in its endio handler so it must be done in its own thread. This makes direct writes quite a bit faster. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com>
2012-05-26Btrfs: dummy extent buffers for tree mod logJan Schmidt1-0/+3
The tree modification log needs two ways to create dummy extent buffers, once by allocating a fresh one (to rebuild an old root) and once by cloning an existing one (to make private rewind modifications) to it. Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
2012-04-18Btrfs: always store the mirror we read the eb fromJosef Bacik1-2/+2
A user reported a panic where we were trying to fix a bad mirror but the mirror number we were giving was 0, which is invalid. This is because we don't do the transid verification until after the read, so as far as the read code is concerned the read was a success. So instead store the mirror we read from so that if there is some failure post read we know which mirror to try next and which mirror needs to be fixed if we find a good copy of the block. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com>
2012-03-28Merge branch 'error-handling' into for-linusChris Mason1-8/+7
Conflicts: fs/btrfs/ctree.c fs/btrfs/disk-io.c fs/btrfs/extent-tree.c fs/btrfs/extent_io.c fs/btrfs/extent_io.h fs/btrfs/inode.c fs/btrfs/scrub.c Signed-off-by: Chris Mason <chris.mason@oracle.com>
2012-03-26Btrfs: deal with read errors on extent buffers differentlyJosef Bacik1-3/+5
Since we need to read and write extent buffers in their entirety we can't use the normal bio_readpage_error stuff since it only works on a per page basis. So instead make it so that if we see an io error in endio we just mark the eb as having an IO error and then in btree_read_extent_buffer_pages we will manually try other mirrors and then overwrite the bad mirror if we find a good copy. This works with larger than page size blocks. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2012-03-26Btrfs: ensure an entire eb is written at onceJosef Bacik1-13/+11
This patch simplifies how we track our extent buffers. Previously we could exit writepages with only having written half of an extent buffer, which meant we had to track the state of the pages and the state of the extent buffers differently. Now we only read in entire extent buffers and write out entire extent buffers, this allows us to simply set bits in our bflags to indicate the state of the eb and we no longer have to do things like track uptodate with our iotree. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2012-03-26Btrfs: introduce free_extent_buffer_staleJosef Bacik1-1/+5
Because btrfs cow's we can end up with extent buffers that are no longer necessary just sitting around in memory. So instead of evicting these pages, we could end up evicting things we actually care about. Thus we have free_extent_buffer_stale for use when we are freeing tree blocks. This will make it so that the ref for the eb being in the radix tree is dropped as soon as possible and then is freed when the refcount hits 0 instead of waiting to be released by releasepage. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com>
2012-03-26Btrfs: set page->private to the ebJosef Bacik1-0/+1
We spend a lot of time looking up extent buffers from pages when we could just store the pointer to the eb the page is associated with in page->private. This patch does just that, and it makes things a little simpler and reduces a bit of CPU overhead involved with doing metadata IO. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com>
2012-03-26Btrfs: allow metadata blocks larger than the page sizeChris Mason1-4/+8
A few years ago the btrfs code to support blocks lager than the page size was disabled to fix a few corner cases in the page cache handling. This fixes the code to properly support large metadata blocks again. Since current kernels will crash early and often with larger metadata blocks, this adds an incompat bit so that older kernels can't mount it. This also does away with different blocksizes for nodes and leaves. You get a single block size for all tree blocks. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2012-03-22btrfs: split extent_state opsJeff Mahoney1-1/+1
set_extent_bit can do exclusive locking but only when called by lock_extent*, Drop the exclusive bits argument except when called by lock_extent. Signed-off-by: Jeff Mahoney <jeffm@suse.com>
2012-03-22btrfs: drop gfp_t from lock_extentJeff Mahoney1-5/+4
lock_extent and unlock_extent are always called with GFP_NOFS, drop the argument and use GFP_NOFS consistently. Signed-off-by: Jeff Mahoney <jeffm@suse.com>
2012-03-22btrfs: return void in functions without error conditionsJeff Mahoney1-2/+2
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
2012-02-15btrfs: delalloc for page dirtied out-of-band in fixup workerJeff Mahoney1-0/+1
We encountered an issue that was easily observable on s/390 systems but could really happen anywhere. The timing just seemed to hit reliably on s/390 with limited memory. The gist is that when an unexpected set_page_dirty() happened, we'd run into the BUG() in btrfs_writepage_fixup_worker since it wasn't properly set up for delalloc. This patch does the following: - Performs the missing delalloc in the fixup worker - Allow the start hook to return -EBUSY which informs __extent_writepage that it should mark the page skipped and not to redirty it. This is required since the fixup worker can fail with -ENOSPC and the page will have already been redirtied. That causes an Oops in drop_outstanding_extents later. Retrying the fixup worker could lead to an infinite loop. Deferring the page redirty also saves us some cycles since the page would be stuck in a resubmit-redirty loop until the fixup worker completes. It's not harmful, just wasteful. - If the fixup worker fails, we mark the page and mapping as errored, and end the writeback, similar to what we would do had the page actually been submitted to writeback. Signed-off-by: Jeff Mahoney <jeffm@suse.com>
2012-01-04Btrfs: add nested locking mode for pathsArne Jansen1-0/+2
This patch adds the possibilty to read-lock an extent even if it is already write-locked from the same thread. btrfs_find_all_roots() needs this capability. Signed-off-by: Arne Jansen <sensille@gmx.net> Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
2011-11-20btrfs: mirror_num should be int, not u64Jan Schmidt1-1/+1
My previous patch introduced some u64 for failed_mirror variables, this one makes it consistent again. Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2011-11-06Merge git://git.jan-o-sch.net/btrfs-unstable into integrationChris Mason1-2/+11
Conflicts: fs/btrfs/Makefile fs/btrfs/extent_io.c fs/btrfs/extent_io.h fs/btrfs/scrub.c Signed-off-by: Chris Mason <chris.mason@oracle.com>
2011-11-06Merge branch 'for-chris' of git://github.com/sensille/linux into integrationChris Mason1-0/+4
Conflicts: fs/btrfs/ctree.h Signed-off-by: Chris Mason <chris.mason@oracle.com>
2011-11-06Btrfs: make sure to flush queued bios if write_cache_pages waitsChris Mason1-1/+2
write_cache_pages tries to build up a large bio to stuff down the pipe. But if it needs to wait for a page lock, it needs to make sure and send down any pending writes so we don't deadlock with anyone who has the page lock and is waiting for writeback of things inside the bio. Dave Sterba triggered this as a deadlock between the autodefrag code and the extent write_cache_pages Signed-off-by: Chris Mason <chris.mason@oracle.com>
2011-10-19Btrfs: stop using write_one_pageJosef Bacik1-0/+1
While looking for a performance regression a user was complaining about, I noticed that we had a regression with the varmail test of filebench. This was introduced by 0d10ee2e6deb5c8409ae65b970846344897d5e4e which keeps us from calling writepages in writepage. This is a correct change, however it happens to help the varmail test because we write out in larger chunks. This is largly to do with how we write out dirty pages for each transaction. If you run filebench with load varmail set $dir=/mnt/btrfs-test run 60 prior to this patch you would get ~1420 ops/second, but with the patch you get ~1200 ops/second. This is a 16% decrease. So since we know the range of dirty pages we want to write out, don't write out in one page chunks, write out in ranges. So to do this we call filemap_fdatawrite_range() on the range of bytes. Then we convert the DIRTY extents to NEED_WAIT extents. When we then call btrfs_wait_marked_extents() we only have to filemap_fdatawait_range() on that range and clear the NEED_WAIT extents. This doesn't get us back to our original speeds, but I've been seeing ~1380 ops/second, which is a <5% regression as opposed to a >15% regression. That is acceptable given that the original commit greatly reduces our latency to begin with. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com>
2011-10-19Btrfs: introduce convert_extent_bitJosef Bacik1-0/+2
If I have a range where I know a certain bit is and I want to set it to another bit the only option I have is to call set and then clear bit, which will result in 2 tree searches. This is inefficient, so introduce convert_extent_bit which will go through and set the bit I want and clear the old bit I don't want. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com>
2011-10-02btrfs: add READAHEAD extent buffer flagArne Jansen1-0/+1
Add a READAHEAD extent buffer flag. Add a function to trigger a read with this flag set. Changes v2: - use extent buffer flags instead of extent state flags Changes v5: - adapt to changed read_extent_buffer_pages interface - don't return eb from reada_tree_block_flagged if it has CORRUPT flag set Signed-off-by: Arne Jansen <sensille@gmx.net>
2011-10-02btrfs: add an extra wait mode to read_extent_buffer_pagesArne Jansen1-0/+3
read_extent_buffer_pages currently has two modes, either trigger a read without waiting for anything, or wait for the I/O to finish. The former also bails when it's unable to lock the page. This patch now adds an additional parameter to allow it to block on page lock, but don't wait for completion. Changes v5: - merge the 2 wait parameters into one and define WAIT_NONE, WAIT_COMPLETE and WAIT_PAGE_LOCK Change v6: - fix bug introduced in v5 Signed-off-by: Arne Jansen <sensille@gmx.net>
2011-09-29btrfs: Moved repair code from inode.c to extent_io.cJan Schmidt1-1/+9
The raid-retry code in inode.c can be generalized so that it works for metadata as well. Thus, this patch moves it to extent_io.c and makes the raid-retry code a raid-repair code. Repair works that way: Whenever a read error occurs and we have more mirrors to try, note the failed mirror, and retry another. If we find a good one, check if we did note a failure earlier and if so, do not allow the read to complete until after the bad sector was written with the good data we just fetched. As we have the extent locked while reading, no one can change the data in between. Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>