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>
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15
fs/dax.c
15
fs/dax.c
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@ -1079,6 +1079,17 @@ static int dax_fault_return(int error)
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return VM_FAULT_SIGBUS;
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}
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/*
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* MAP_SYNC on a dax mapping guarantees dirty metadata is
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* flushed on write-faults (non-cow), but not read-faults.
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*/
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static bool dax_fault_is_synchronous(unsigned long flags,
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struct vm_area_struct *vma, struct iomap *iomap)
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{
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return (flags & IOMAP_WRITE) && (vma->vm_flags & VM_SYNC)
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&& (iomap->flags & IOMAP_F_DIRTY);
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}
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static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
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const struct iomap_ops *ops)
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{
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@ -1170,7 +1181,7 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
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goto finish_iomap;
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}
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sync = (vma->vm_flags & VM_SYNC) && (iomap.flags & IOMAP_F_DIRTY);
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sync = dax_fault_is_synchronous(flags, vma, &iomap);
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switch (iomap.type) {
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case IOMAP_MAPPED:
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@ -1390,7 +1401,7 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
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if (iomap.offset + iomap.length < pos + PMD_SIZE)
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goto finish_iomap;
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sync = (vma->vm_flags & VM_SYNC) && (iomap.flags & IOMAP_F_DIRTY);
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sync = dax_fault_is_synchronous(iomap_flags, vma, &iomap);
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switch (iomap.type) {
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case IOMAP_MAPPED:
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@ -3479,7 +3479,7 @@ retry:
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}
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iomap->flags = 0;
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if ((flags & IOMAP_WRITE) && ext4_inode_datasync_dirty(inode))
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if (ext4_inode_datasync_dirty(inode))
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iomap->flags |= IOMAP_F_DIRTY;
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iomap->bdev = inode->i_sb->s_bdev;
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iomap->dax_dev = sbi->s_daxdev;
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@ -1087,8 +1087,8 @@ xfs_file_iomap_begin(
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trace_xfs_iomap_found(ip, offset, length, 0, &imap);
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}
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if ((flags & IOMAP_WRITE) && xfs_ipincount(ip) &&
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(ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
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if (xfs_ipincount(ip) && (ip->i_itemp->ili_fsync_fields
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& ~XFS_ILOG_TIMESTAMP))
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iomap->flags |= IOMAP_F_DIRTY;
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xfs_bmbt_to_iomap(ip, iomap, &imap);
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