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2011-01-16Merge branch 'readonly-snapshots' of git://repo.or.cz/linux-btrfs-devel into ↵Chris Mason
btrfs-38
2011-01-04Btrfs: fix off by one while setting block groups readonlyChris Mason
When we read in block groups, we'll set non-redundant groups readonly if we find a raid1, DUP or raid10 group. But the ro code has an off by one bug in the math around testing to make sure out accounting doesn't go wrong. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-12-23Btrfs: Add BTRFS_IOC_SUBVOL_GETFLAGS/SETFLAGS ioctlsLi Zefan
This allows us to set a snapshot or a subvolume readonly or writable on the fly. Usage: Set BTRFS_SUBVOL_RDONLY of btrfs_ioctl_vol_arg_v2->flags, and then call ioctl(BTRFS_IOCTL_SUBVOL_SETFLAGS); Changelog for v3: - Change to pass __u64 as ioctl parameter. Changelog for v2: - Add _GETFLAGS ioctl. - Check if the passed fd is the root of a subvolume. - Change the name from _SNAP_SETFLAGS to _SUBVOL_SETFLAGS. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
2010-12-23Btrfs: Add readonly snapshots supportLi Zefan
Usage: Set BTRFS_SUBVOL_RDONLY of btrfs_ioctl_vol_arg_v2->flags, and call ioctl(BTRFS_I0CTL_SNAP_CREATE_V2). Implementation: - Set readonly bit of btrfs_root_item->flags. - Add readonly checks in btrfs_permission (inode_permission), btrfs_setattr, btrfs_set/remove_xattr and some ioctls. Changelog for v3: - Eliminate btrfs_root->readonly, but check btrfs_root->root_item.flags. - Rename BTRFS_ROOT_SNAP_RDONLY to BTRFS_ROOT_SUBVOL_RDONLY. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
2010-12-23Btrfs: Refactor btrfs_ioctl_snap_create()Li Zefan
Split it into two functions for two different ioctls, since they share no common code. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
2010-12-14Btrfs: prevent RAID level downgrades when space is lowChris Mason
The extent allocator has code that allows us to fill allocations from any available block group, even if it doesn't match the raid level we've requested. This was put in because adding a new drive to a filesystem made with the default mkfs options actually upgrades the metadata from single spindle dup to full RAID1. But, the code also allows us to allocate from a raid0 chunk when we really want a raid1 or raid10 chunk. This can cause big trouble because mkfs creates a small (4MB) raid0 chunk for data and metadata which then goes unused for raid1/raid10 installs. The allocator will happily wander in and allocate from that chunk when things get tight, which is not correct. The fix here is to make sure that we provide duplication when the caller has asked for it. It does all the dups to be any raid level, which preserves the dup->raid1 upgrade abilities. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-12-14Btrfs: account for missing devices in RAID allocation profilesChris Mason
When we mount in RAID degraded mode without adding a new device to replace the failed one, we can end up using the wrong RAID flags for allocations. This results in strange combinations of block groups (raid1 in a raid10 filesystem) and corruptions when we try to allocate blocks from single spindle chunks on drives that are actually missing. The first device has two small 4MB chunks in it that mkfs creates and these are usually unused in a raid1 or raid10 setup. But, in -o degraded, the allocator will fall back to these because the mask of desired raid groups isn't correct. The fix here is to count the missing devices as we build up the list of devices in the system. This count is used when picking the raid level to make sure we continue using the same levels that were in place before we lost a drive. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-12-13Btrfs: EIO when we fail to read tree rootsChris Mason
If we just get a plain IO error when we read tree roots, the code wasn't properly sending that error up the chain. This allowed mounts to continue when they should failed, and allowed operations on partially setup root structs. The end result was usually oopsen on spinlocks that hadn't been spun up correctly. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-12-10Btrfs: fix compiler warningsJan Beulich
... regarding an unused function when !MIGRATION, and regarding a printk() format string vs argument mismatch. Signed-off-by: Jan Beulich <jbeulich@novell.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-12-10Btrfs: Make async snapshot ioctl more genericLi Zefan
If we had reserved some bytes in struct btrfs_ioctl_vol_args, we wouldn't have to create a new structure for async snapshot creation. Here we convert async snapshot ioctl to use a more generic ABI, as we'll add more ioctls for snapshots/subvolumes in the future, readonly snapshots for example. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-12-10Btrfs: pwrite blocked when writing from the mmaped buffer of the same pageXin Zhong
This problem is found in meego testing: http://bugs.meego.com/show_bug.cgi?id=6672 A file in btrfs is mmaped and the mmaped buffer is passed to pwrite to write to the same page of the same file. In btrfs_file_aio_write(), the pages is locked by prepare_pages(). So when btrfs_copy_from_user() is called, page fault happens and the same page needs to be locked again in filemap_fault(). The fix is to move iov_iter_fault_in_readable() before prepage_pages() to make page fault happen before pages are locked. And also disable page fault in critical region in btrfs_copy_from_user(). Reviewed-by: Yan, Zheng<zheng.z.yan@intel.com> Signed-off-by: Zhong, Xin <xin.zhong@intel.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-12-10Btrfs: Fix a crash when mounting a subvolumeLi Zefan
We should drop dentry before deactivating the superblock, otherwise we can hit this bug: BUG: Dentry f349a690{i=100,n=/} still in use (1) [unmount of btrfs loop1] ... Steps to reproduce the bug: # mount /dev/loop1 /mnt # mkdir save # btrfs subvolume snapshot /mnt save/snap1 # umount /mnt # mount -o subvol=save/snap1 /dev/loop1 /mnt (crash) Reported-by: Michael Niederle <mniederle@gmx.at> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-12-10Btrfs: fix sync subvol/snapshot creationSage Weil
We were incorrectly taking the async path even for the sync ioctls by passing in &transid unconditionally. There's ample room for further cleanup here, but this keeps the fix simple. Signed-off-by: Sage Weil <sage@newdream.net> Reviewed-by: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-12-10Btrfs: Fix page leak in compressed writeback pathYan, Zheng
"start + num_bytes >= actual_end" can happen when compressed page writeback races with file truncation. In that case we need unlock and release pages past the end of file. Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-12-10Btrfs: do not BUG if we fail to remove the orphan item for dead snapshotsJosef Bacik
Not being able to delete an orphan item isn't a horrible thing. The worst that happens is the next time around we try and do the orphan cleanup and we can't find the referenced object and just delete the item and move on. Signed-off-by: Josef Bacik <josef@redhat.com>
2010-12-09Btrfs: fixup return code for btrfs_del_orphan_itemJosef Bacik
If the orphan item doesn't exist, we return 1, which doesn't make any sense to the callers. Instead return -ENOENT if we didn't find the item. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com>
2010-12-09Btrfs: do not do fast caching if we are allocating blocks for tree_rootJosef Bacik
Since the fast caching uses normal tree locking, we can possibly deadlock if we get to the caching via a btrfs_search_slot() on the tree_root. So just check to see if the root we are on is the tree root, and just don't do the fast caching. Reported-by: Sage Weil <sage@newdream.net> Signed-off-by: Josef Bacik <josef@redhat.com>
2010-12-09Btrfs: deal with space cache errors betterJosef Bacik
Currently if the space cache inode generation number doesn't match the generation number in the space cache header we will just fail to load the space cache, but we won't mark the space cache as an error, so we'll keep getting that error each time somebody tries to cache that block group until we actually clear the thing. Fix this by marking the space cache as having an error so we only get the message once. This patch also makes it so that we don't try and setup space cache for a block group that isn't cached, since we won't be able to write it out anyway. None of these problems are actual problems, they are just annoying and sub-optimal. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com>
2010-12-09Btrfs: fix use after free in O_DIRECTJosef Bacik
This fixes a bug where we use dip after we have freed it. Instead just use the file_offset that was passed to the function. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com>
2010-11-29Btrfs: don't use migrate page without CONFIG_MIGRATIONChris Mason
Fixes compile error Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-29Btrfs: deal with DIO bios that span more than one ordered extentChris Mason
The new DIO bio splitting code has problems when the bio spans more than one ordered extent. This will happen as the generic DIO code merges our get_blocks calls together into a bigger single bio. This fixes things by walking forward in the ordered extent code finding all the overlapping ordered extents and completing them all at once. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-27Btrfs: setup blank root and fs_info for mount timeJosef Bacik
There is a problem with how we use sget, it searches through the list of supers attached to the fs_type looking for a super with the same fs_devices as what we're trying to mount. This depends on sb->s_fs_info being filled, but we don't fill that in until we get to btrfs_fill_super, so we could hit supers on the fs_type super list that have a null s_fs_info. In order to fix that we need to go ahead and setup a blank root with a blank fs_info to hold fs_devices, that way our test will work out right and then we can set s_fs_info in btrfs_set_super, and then open_ctree will simply use our pre-allocated root and fs_info when setting everything up. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-27Btrfs: fix fiemapJosef Bacik
There are two big problems currently with FIEMAP 1) We return extents for holes. This isn't supposed to happen, we just don't return extents for holes and then userspace interprets the lack of an extent as a hole. 2) We sometimes don't set FIEMAP_EXTENT_LAST properly. This is because we wait to see a EXTENT_FLAG_VACANCY flag on the em, but this won't happen if say we ask fiemap to map up to the last extent in a file, and there is nothing but holes up to the i_size. To fix this we need to lookup the last extent in this file and save the logical offset, so if we happen to try and map that extent we can be sure to set FIEMAP_EXTENT_LAST. With this patch we now pass xfstest 225, which we never have before. Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-27Btrfs - fix race between btrfs_get_sb() and umountIan Kent
When mounting a btrfs file system btrfs_test_super() may attempt to use sb->s_fs_info, the btrfs root, of a super block that is going away and that has had the btrfs root set to NULL in its ->put_super(). But if the super block is going away it cannot be an existing super block so we can return false in this case. Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-27Btrfs: update inode ctime when using linksJosef Bacik
Currently we fail xfstest 236 because we're not updating the inode ctime on link. This is a simple fix, and makes it so we pass 236 now. Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-27Btrfs: make sure new inode size is ok in fallocateJosef Bacik
We have been failing xfstest 228 forever, because we don't check to make sure the new inode size is acceptable as far as RLIMIT is concerned. Just check to make sure it's ok to create a inode with this new size and error out if not. With this patch we now pass 228. Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-27Btrfs: fix typo in fallocate to make it honor actual sizeJosef Bacik
There is a typo in __btrfs_prealloc_file_range() where we set the i_size to actual_len/cur_offset, and then just set it to cur_offset again, and do the same with btrfs_ordered_update_i_size(). This fixes it back to keeping i_size in a local variable and then updating i_size properly. Tested this with xfs_io -F -f -c "falloc 0 1" -c "pwrite 0 1" foo stat'ing foo gives us a size of 1 instead of 4096 like it was. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-22Btrfs: avoid NULL pointer deref in try_release_extent_bufferChris Mason
If we fail to find a pointer in the radix tree, don't try to deref the NULL one we do have. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-22Btrfs: make btrfs_add_nondir take parent inode as an argumentJosef Bacik
Everybody who calls btrfs_add_nondir just passes in the dentry of the new file and then dereference dentry->d_parent->d_inode, but everybody who calls btrfs_add_nondir() are already passed the parent's inode. So instead of dereferencing dentry->d_parent, just make btrfs_add_nondir take the dir inode as an argument and pass that along so we don't have to worry about d_parent. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-22Btrfs: hold i_mutex when calling btrfs_log_dentry_safeJosef Bacik
Since we walk up the path logging all of the parts of the inode's path, we need to hold i_mutex to make sure that the inode is not renamed while we're logging everything. btrfs_log_dentry_safe does dget_parent and all of that jazz, but we may get unexpected results if the rename changes the inode's location while we're higher up the path logging those dentries, so do this for safety reasons. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-22Btrfs: use dget_parent where we can UPDATEDJosef Bacik
There are lots of places where we do dentry->d_parent->d_inode without holding the dentry->d_lock. This could cause problems with rename. So instead we need to use dget_parent() and hold the reference to the parent as long as we are going to use it's inode and then dput it at the end. Signed-off-by: Josef Bacik <josef@redhat.com> Cc: raven@themaw.net Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-22Btrfs: fix more ESTALE problems with NFSJosef Bacik
When creating new inodes we don't setup inode->i_generation. So if we generate an fh with a newly created inode we save the generation of 0, but if we flush the inode to disk and have to read it back when getting the inode on the server we'll have the right i_generation, so gens wont match and we get ESTALE. This patch properly sets inode->i_generation when we create the new inode and now I'm no longer getting ESTALE. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-22Btrfs: handle NFS lookups properlyJosef Bacik
People kept reporting NFS issues, specifically getting ESTALE alot. I figured out how to reproduce the problem SERVER mkfs.btrfs /dev/sda1 mount /dev/sda1 /mnt/btrfs-test <add /mnt/btrfs-test to /etc/exports> btrfs subvol create /mnt/btrfs-test/foo service nfs start CLIENT mount server:/mnt/btrfs /mnt/test cd /mnt/test/foo ls SERVER echo 3 > /proc/sys/vm/drop_caches CLIENT ls <-- get an ESTALE here This is because the standard way to lookup a name in nfsd is to use readdir, and what it does is do a readdir on the parent directory looking for the inode of the child. So in this case the parent being / and the child being foo. Well subvols all have the same inode number, so doing a readdir of / looking for inode 256 will return '.', which obviously doesn't match foo. So instead we need to have our own .get_name so that we can find the right name. Our .get_name will either lookup the inode backref or the root backref, whichever we're looking for, and return the name we find. Running the above reproducer with this patch results in everything acting the way its supposed to. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-22btrfs: make 1-bit signed fileds unsignedMariusz Kozlowski
Fixes these sparse warnings: fs/btrfs/ctree.h:811:17: error: dubious one-bit signed bitfield fs/btrfs/ctree.h:812:20: error: dubious one-bit signed bitfield fs/btrfs/ctree.h:813:19: error: dubious one-bit signed bitfield Signed-off-by: Mariusz Kozlowski <mk@lab.zgora.pl> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-22btrfs: Show device attr correctly for symlinksLi Zefan
Symlinks and files of other types show different device numbers, though they are on the same partition: $ touch tmp; ln -s tmp tmp2; stat tmp tmp2 File: `tmp' Size: 0 Blocks: 0 IO Block: 4096 regular empty file Device: 15h/21d Inode: 984027 Links: 1 --- snip --- File: `tmp2' -> `tmp' Size: 3 Blocks: 0 IO Block: 4096 symbolic link Device: 13h/19d Inode: 984028 Links: 1 Reported-by: Toke Høiland-Jørgensen <toke@toke.dk> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-22btrfs: Set file size correctly in file cloneLi Zefan
Set src_offset = 0, src_length = 20K, dest_offset = 20K. And the original filesize of the dest file 'file2' is 30K: # ls -l /mnt/file2 -rw-r--r-- 1 root root 30720 Nov 18 16:42 /mnt/file2 Now clone file1 to file2, the dest file should be 40K, but it still shows 30K: # ls -l /mnt/file2 -rw-r--r-- 1 root root 30720 Nov 18 16:42 /mnt/file2 Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-22btrfs: Check if dest_offset is block-size aligned before cloning fileLi Zefan
We've done the check for src_offset and src_length, and We should also check dest_offset, otherwise we'll corrupt the destination file: (After cloning file1 to file2 with unaligned dest_offset) # cat /mnt/file2 cat: /mnt/file2: Input/output error Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-22Btrfs: handle the space_cache option properlyJosef Bacik
When I added the clear_cache option I screwed up and took the break out of the space_cache case statement, so whenever you mount with space_cache you also get clear_cache, which does you no good if you say set space_cache in fstab so it always gets set. This patch adds the break back in properly. Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-22btrfs: Fix early enospc because 'unused' calculated with wrong sign.Arne Jansen
'unused' calculated with wrong sign in reserve_metadata_bytes(). This might have lead to unwanted over-reservations. Signed-off-by: Arne Jansen <sensille@gmx.net> Reviewed-by: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-22btrfs: fix panic caused by direct IOMiao Xie
btrfs paniced when we write >64KB data by direct IO at one time. Reproduce steps: # mkfs.btrfs /dev/sda5 /dev/sda6 # mount /dev/sda5 /mnt # dd if=/dev/zero of=/mnt/tmpfile bs=100K count=1 oflag=direct Then btrfs paniced: mapping failed logical 1103155200 bio len 69632 len 12288 ------------[ cut here ]------------ kernel BUG at fs/btrfs/volumes.c:3010! [SNIP] Pid: 1992, comm: btrfs-worker-0 Not tainted 2.6.37-rc1 #1 D2399/PRIMERGY RIP: 0010:[<ffffffffa03d1462>] [<ffffffffa03d1462>] btrfs_map_bio+0x202/0x210 [btrfs] [SNIP] Call Trace: [<ffffffffa03ab3eb>] __btrfs_submit_bio_done+0x1b/0x20 [btrfs] [<ffffffffa03a35ff>] run_one_async_done+0x9f/0xb0 [btrfs] [<ffffffffa03d3d20>] run_ordered_completions+0x80/0xc0 [btrfs] [<ffffffffa03d45a4>] worker_loop+0x154/0x5f0 [btrfs] [<ffffffffa03d4450>] ? worker_loop+0x0/0x5f0 [btrfs] [<ffffffffa03d4450>] ? worker_loop+0x0/0x5f0 [btrfs] [<ffffffff81083216>] kthread+0x96/0xa0 [<ffffffff8100cec4>] kernel_thread_helper+0x4/0x10 [<ffffffff81083180>] ? kthread+0x0/0xa0 [<ffffffff8100cec0>] ? kernel_thread_helper+0x0/0x10 We fix this problem by splitting bios when we submit bios. Reported-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com> Signed-off-by: Miao Xie <miaox@cn.fujitsu.com> Tested-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-22btrfs: cleanup duplicate bio allocating functionsMiao Xie
extent_bio_alloc() and compressed_bio_alloc() are similar, cleanup similar source code. Signed-off-by: Miao Xie <miaox@cn.fujitsu.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-22btrfs: fix free dip and dip->csums twiceMiao Xie
bio_endio() will free dip and dip->csums, so dip and dip->csums twice will be freed twice. Fix it. Signed-off-by: Miao Xie <miaox@cn.fujitsu.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-11-22Btrfs: add migrate page for metadata inodeChris Mason
Migrate page will directly call the btrfs btree writepage function, which isn't actually allowed. Our writepage assumes that you have locked the extent_buffer and flagged the block as written. Without doing these steps, we can corrupt metadata blocks. A later commit will remove the btree writepage function since it is really only safely used internally by btrfs. We use writepages for everything else. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-10-30Btrfs: deal with errors from updating the tree logChris Mason
During unlink we remove any references to the inode from the tree log. It can return -ENOENT and other errors, and this changes the unlink code to deal with it. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-10-30Btrfs: allow subvol deletion by unprivileged user with -o user_subvol_rm_allowedSage Weil
Add a mount option user_subvol_rm_allowed that allows users to delete a (potentially non-empty!) subvol when they would otherwise we allowed to do an rmdir(2). We duplicate the may_delete() checks from the core VFS code to implement identical security checks (minus the directory size check). We additionally require that the user has write+exec permission on the subvol root inode. Signed-off-by: Sage Weil <sage@newdream.net> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-10-30Btrfs: make SNAP_DESTROY asyncSage Weil
There is no reason to force an immediate commit when deleting a snapshot. Users have some expectation that space from a deleted snapshot be freed immediately, but even if we do commit the reclaim is a background process. If users _do_ want the deletion to be durable, they can call 'sync'. Signed-off-by: Sage Weil <sage@newdream.net> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-10-30Btrfs: add SNAP_CREATE_ASYNC ioctlSage Weil
Create a snap without waiting for it to commit to disk. The ioctl is ordered such that subsequent operations will not be contained by the created snapshot, and the commit is initiated, but the ioctl does not wait for the snapshot to commit to disk. We return the specific transid to userspace so that an application can wait for this specific snapshot creation to commit via the WAIT_SYNC ioctl. Signed-off-by: Sage Weil <sage@newdream.net> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-10-29Btrfs: add START_SYNC, WAIT_SYNC ioctlsSage Weil
START_SYNC will start a sync/commit, but not wait for it to complete. Any modification started after the ioctl returns is guaranteed not to be included in the commit. If a non-NULL pointer is passed, the transaction id will be returned to userspace. WAIT_SYNC will wait for any in-progress commit to complete. If a transaction id is specified, the ioctl will block and then return (success) when the specified transaction has committed. If it has already committed when we call the ioctl, it returns immediately. If the specified transaction doesn't exist, it returns EINVAL. If no transaction id is specified, WAIT_SYNC will wait for the currently committing transaction to finish it's commit to disk. If there is no currently committing transaction, it returns success. These ioctls are useful for applications which want to impose an ordering on when fs modifications reach disk, but do not want to wait for the full (slow) commit process to do so. Picky callers can take the transid returned by START_SYNC and feed it to WAIT_SYNC, and be certain to wait only as long as necessary for the transaction _they_ started to reach disk. Sloppy callers can START_SYNC and WAIT_SYNC without a transid, and provided they didn't wait too long between the calls, they will get the same result. However, if a second commit starts before they call WAIT_SYNC, they may end up waiting longer for it to commit as well. Even so, a START_SYNC+WAIT_SYNC still guarantees that any operation completed before the START_SYNC reaches disk. Signed-off-by: Sage Weil <sage@newdream.net> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-10-29Btrfs: async transaction commitSage Weil
Add support for an async transaction commit that is ordered such that any subsequent operations will join the following transaction, but does not wait until the current commit is fully on disk. This avoids much of the latency associated with the btrfs_commit_transaction for callers concerned with serialization and not safety. The wait_for_unblock flag controls whether we wait for the 'middle' portion of commit_transaction to complete, which is necessary if the caller expects some of the modifications contained in the commit to be available (this is the case for subvol/snapshot creation). Signed-off-by: Sage Weil <sage@newdream.net> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-10-29Btrfs: fix deadlock in btrfs_commit_transactionSage Weil
We calculate timeout (either 1 or MAX_SCHEDULE_TIMEOUT) based on whether num_writers > 1 or should_grow at the top of the loop. Then, much much later, we wait for that timeout if either num_writers or should_grow is true. However, it's possible for a racing process (calling btrfs_end_transaction()) to decrement num_writers such that we wait forever instead of for 1. Fix this by deciding how long to wait when we wait. Include a smp_mb() before checking if the waitqueue is active to ensure the num_writers is visible. Signed-off-by: Sage Weil <sage@newdream.net> Signed-off-by: Chris Mason <chris.mason@oracle.com>