kernel.git/fs/xfs/xfs_alloc.c, branch linux-3.11.y

xfs: Avoid pathological backwards allocation

2013-05-20T18:09:11Z

Writing a large file using direct IO in 16 MB chunks sometimes results in a pathological allocation pattern where 16 MB chunks of large free extent are allocated to a file in a reversed order. So extents of a file look for example as: ext logical physical expected length flags 0 0 13 4550656 1 4550656 188136807 4550668 12562432 2 17113088 200699240 200699238 622592 3 17735680 182046055 201321831 4096 4 17739776 182041959 182050150 4096 5 17743872 182037863 182046054 4096 6 17747968 182033767 182041958 4096 7 17752064 182029671 182037862 4096 ... 6757 45400064 154381644 154389835 4096 6758 45404160 154377548 154385739 4096 6759 45408256 252951571 154381643 73728 eof This happens because XFS_ALLOCTYPE_THIS_BNO allocation fails (the last extent in the file cannot be further extended) so we fall back to XFS_ALLOCTYPE_NEAR_BNO allocation which picks end of a large free extent as the best place to continue the file. Since the chunk at the end of the free extent again cannot be further extended, this behavior repeats until the whole free extent is consumed in a reversed order. For data allocations this backward allocation isn't beneficial so make xfs_alloc_compute_diff() pick start of a free extent instead of its end for them. That avoids the backward allocation pattern. See thread at http://oss.sgi.com/archives/xfs/2013-03/msg00144.html for more details about the reproduction case and why this solution was chosen. Based on idea by Dave Chinner . CC: Dave Chinner Signed-off-by: Jan Kara Reviewed-by: Dave Chinner Reviewed-by: Mark Tinguely Signed-off-by: Ben Myers

xfs: buffer type overruns blf_flags field

2013-04-27T18:01:58Z

The buffer type passed to log recvoery in the buffer log item overruns the blf_flags field. I had assumed that flags field was a 32 bit value, and it turns out it is a unisgned short. Therefore having 19 flags doesn't really work. Convert the buffer type field to numeric value, and use the top 5 bits of the flags field for it. We currently have 17 types of buffers, so using 5 bits gives us plenty of room for expansion in future.... Signed-off-by: Dave Chinner Reviewed-by: Ben Myers Signed-off-by: Ben Myers

xfs: add CRC checks to the AGFL

2013-04-21T19:55:34Z

Add CRC checks, location information and a magic number to the AGFL. Previously the AGFL was just a block containing nothing but the free block pointers. The new AGFL has a real header with the usual boilerplate instead, so that we can verify it's not corrupted and written into the right place. [dchinner@redhat.com] Added LSN field, reworked significantly to fit into new verifier structure and growfs structure, enabled full verifier functionality now there is a header to verify and we can guarantee an initialised AGFL. Signed-off-by: Christoph Hellwig Signed-off-by: Dave Chinner Reviewed-by: Ben Myers Signed-off-by: Ben Myers

xfs: add CRC checks to the AGF

2013-04-21T19:54:46Z

The AGF already has some self identifying fields (e.g. the sequence number) so we only need to add the uuid to it to identify the filesystem it belongs to. The location is fixed based on the sequence number, so there's no need to add a block number, either. Hence the only additional fields are the CRC and LSN fields. These are unlogged, so place some space between the end of the logged fields and them so that future expansion of the AGF for logged fields can be placed adjacent to the existing logged fields and hence not complicate the field-derived range based logging we currently have. Based originally on a patch from myself, modified further by Christoph Hellwig and then modified again to fit into the verifier structure with additional fields by myself. The multiple signed-off-by tags indicate the age and history of this patch. Signed-off-by: Dave Chinner Signed-off-by: Christoph Hellwig Signed-off-by: Dave Chinner Reviewed-by: Ben Myers Signed-off-by: Ben Myers

xfs: rename random32() to prandom_u32()

2013-03-07T18:33:57Z

Use more preferable function name which implies using a pseudo-random number generator. Signed-off-by: Akinobu Mita Acked-by: Cc: Ben Myers Cc: Alex Elder Cc: xfs@oss.sgi.com Signed-off-by: Ben Myers

xfs: don't zero structure members after a memset(0)

2013-01-03T22:00:07Z

Commit 408cc4e97a3ccd172d2d676e4b585badf439271b added memset(0, ...) to allocation args structures, so there is no need to explicitly set any of the fields to 0 after that. Signed-off-by: Eric Sandeen Reviewed-by: Mark Tinguely Signed-off-by: Ben Myers

xfs: convert buffer verifiers to an ops structure.

2012-11-16T03:35:12Z

To separate the verifiers from iodone functions and associate read and write verifiers at the same time, introduce a buffer verifier operations structure to the xfs_buf. This avoids the need for assigning the write verifier, clearing the iodone function and re-running ioend processing in the read verifier, and gets rid of the nasty "b_pre_io" name for the write verifier function pointer. If we ever need to, it will also be easier to add further content specific callbacks to a buffer with an ops structure in place. We also avoid needing to export verifier functions, instead we can simply export the ops structures for those that are needed outside the function they are defined in. This patch also fixes a directory block readahead verifier issue it exposed. This patch also adds ops callbacks to the inode/alloc btree blocks initialised by growfs. These will need more work before they will work with CRCs. Signed-off-by: Dave Chinner Reviewed-by: Phil White Signed-off-by: Ben Myers

xfs: connect up write verifiers to new buffers

2012-11-16T03:35:09Z

Metadata buffers that are read from disk have write verifiers already attached to them, but newly allocated buffers do not. Add appropriate write verifiers to all new metadata buffers. Signed-off-by: Dave Chinner Reviewed-by: Ben Myers Signed-off-by: Ben Myers

xfs: add pre-write metadata buffer verifier callbacks

2012-11-16T03:35:02Z

These verifiers are essentially the same code as the read verifiers, but do not require ioend processing. Hence factor the read verifier functions and add a new write verifier wrapper that is used as the callback. This is done as one large patch for all verifiers rather than one patch per verifier as the change is largely mechanical. This includes hooking up the write verifier via the read verifier function. Hooking up the write verifier for buffers obtained via xfs_trans_get_buf() will be done in a separate patch as that touches code in many different places rather than just the verifier functions. Signed-off-by: Dave Chinner Reviewed-by: Mark Tinguely Signed-off-by: Ben Myers

xfs: verify AGFL blocks as they are read from disk

2012-11-16T03:34:14Z

Add an AGFL block verify callback function and pass it into the buffer read functions. While this commit adds verification code to the AGFL, it cannot be used reliably until the CRC format change comes along as mkfs does not initialise the full AGFL. Hence it can be full of garbage at the first mount and will fail verification right now. CRC enabled filesystems won't have this problem, so leave the code that has already been written ifdef'd out until the proper time. Signed-off-by: Dave Chinner Reviewed-by: Phil White Signed-off-by: Ben Myers