From aaa422c4c3f6ee958ea9d6c9260ac40f90a3f4e9 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Mon, 13 Nov 2017 16:38:44 -0800 Subject: 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 Reviewed-by: Christoph Hellwig Reviewed-by: Darrick J. Wong Cc: Ross Zwisler Reported-by: Dave Chinner Signed-off-by: Dan Williams --- fs/dax.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) (limited to 'fs/dax.c') diff --git a/fs/dax.c b/fs/dax.c index 78233c716757..27ba300660ff 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -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: -- cgit