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| author | Dave Chinner <dchinner@redhat.com> | 2018-06-07 07:46:42 -0700 |
|---|---|---|
| committer | Darrick J. Wong <darrick.wong@oracle.com> | 2018-06-08 10:07:51 -0700 |
| commit | 4a2d01b076d231afebbea04647373644e767b453 (patch) | |
| tree | cbc2479bf4ca80dc56e6b67beb77a28d3415eae0 /fs/xfs | |
| parent | ef215e394eeb960ea0e8a0fd37ba2fa30260e05b (diff) | |
| download | lwn-4a2d01b076d231afebbea04647373644e767b453.tar.gz lwn-4a2d01b076d231afebbea04647373644e767b453.zip | |
xfs: xfs_reflink_convert_cow() memory allocation deadlock
xfs_reflink_convert_cow() manipulates the incore extent list
in GFP_KERNEL context in the IO submission path whilst holding
locked pages under writeback. This is a memory reclaim deadlock
vector. This code is not in a transaction, so any memory allocations
it makes aren't protected via the memalloc_nofs_save() context that
transactions carry.
Hence we need to run this call under memalloc_nofs_save() context to
prevent potential memory allocations from being run as GFP_KERNEL
and deadlocking.
Signed-Off-By: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Diffstat (limited to 'fs/xfs')
| -rw-r--r-- | fs/xfs/xfs_aops.c | 11 | ||||
| -rw-r--r-- | fs/xfs/xfs_buf.c | 1 | ||||
| -rw-r--r-- | fs/xfs/xfs_linux.h | 1 |
3 files changed, 12 insertions, 1 deletions
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c index 767d53222f31..1eb625fdcb1e 100644 --- a/fs/xfs/xfs_aops.c +++ b/fs/xfs/xfs_aops.c @@ -531,8 +531,19 @@ xfs_submit_ioend( { /* Convert CoW extents to regular */ if (!status && ioend->io_type == XFS_IO_COW) { + /* + * Yuk. This can do memory allocation, but is not a + * transactional operation so everything is done in GFP_KERNEL + * context. That can deadlock, because we hold pages in + * writeback state and GFP_KERNEL allocations can block on them. + * Hence we must operate in nofs conditions here. + */ + unsigned nofs_flag; + + nofs_flag = memalloc_nofs_save(); status = xfs_reflink_convert_cow(XFS_I(ioend->io_inode), ioend->io_offset, ioend->io_size); + memalloc_nofs_restore(nofs_flag); } /* Reserve log space if we might write beyond the on-disk inode size. */ diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c index 980bc48979e9..e9c058e3761c 100644 --- a/fs/xfs/xfs_buf.c +++ b/fs/xfs/xfs_buf.c @@ -21,7 +21,6 @@ #include <linux/migrate.h> #include <linux/backing-dev.h> #include <linux/freezer.h> -#include <linux/sched/mm.h> #include "xfs_format.h" #include "xfs_log_format.h" diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h index ae1e66fa3f61..1631cf4546f2 100644 --- a/fs/xfs/xfs_linux.h +++ b/fs/xfs/xfs_linux.h @@ -26,6 +26,7 @@ typedef __u32 xfs_nlink_t; #include <linux/semaphore.h> #include <linux/mm.h> +#include <linux/sched/mm.h> #include <linux/kernel.h> #include <linux/blkdev.h> #include <linux/slab.h> |