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| author | Dan Williams <dan.j.williams@intel.com> | 2017-11-13 16:38:44 -0800 |
|---|---|---|
| committer | Dan Williams <dan.j.williams@intel.com> | 2017-11-13 16:38:44 -0800 |
| commit | aaa422c4c3f6ee958ea9d6c9260ac40f90a3f4e9 (patch) | |
| tree | 64ce62bb891f903a5c504a2700823cbd60bb877c /fs/dax.c | |
| parent | a39e596baa07cb1dc19c2ead14c9fd2a30f22352 (diff) | |
| download | lwn-aaa422c4c3f6ee958ea9d6c9260ac40f90a3f4e9.tar.gz lwn-aaa422c4c3f6ee958ea9d6c9260ac40f90a3f4e9.zip | |
fs, dax: unify IOMAP_F_DIRTY read vs write handling policy in the dax core
While reviewing whether MAP_SYNC should strengthen its current guarantee
of syncing writes from the initiating process to also include
third-party readers observing dirty metadata, Dave pointed out that the
check of IOMAP_WRITE is misplaced.
The policy of what to with IOMAP_F_DIRTY should be separated from the
generic filesystem mechanism of reporting dirty metadata. Move this
policy to the fs-dax core to simplify the per-filesystem iomap handlers,
and further centralize code that implements the MAP_SYNC policy. This
otherwise should not change behavior, it just makes it easier to change
behavior in the future.
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Reported-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'fs/dax.c')
| -rw-r--r-- | fs/dax.c | 15 |
1 files changed, 13 insertions, 2 deletions
@@ -1079,6 +1079,17 @@ static int dax_fault_return(int error) return VM_FAULT_SIGBUS; } +/* + * MAP_SYNC on a dax mapping guarantees dirty metadata is + * flushed on write-faults (non-cow), but not read-faults. + */ +static bool dax_fault_is_synchronous(unsigned long flags, + struct vm_area_struct *vma, struct iomap *iomap) +{ + return (flags & IOMAP_WRITE) && (vma->vm_flags & VM_SYNC) + && (iomap->flags & IOMAP_F_DIRTY); +} + static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp, const struct iomap_ops *ops) { @@ -1170,7 +1181,7 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp, goto finish_iomap; } - sync = (vma->vm_flags & VM_SYNC) && (iomap.flags & IOMAP_F_DIRTY); + sync = dax_fault_is_synchronous(flags, vma, &iomap); switch (iomap.type) { case IOMAP_MAPPED: @@ -1390,7 +1401,7 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp, if (iomap.offset + iomap.length < pos + PMD_SIZE) goto finish_iomap; - sync = (vma->vm_flags & VM_SYNC) && (iomap.flags & IOMAP_F_DIRTY); + sync = dax_fault_is_synchronous(iomap_flags, vma, &iomap); switch (iomap.type) { case IOMAP_MAPPED: |