linux-ext4 - Re: [PATCH v8 17/19] xfs: add pre-content fsnotify hook for write faults

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Message-ID: <20241121102248.w3jkpcn3wosxbh62@quack3>
Date: Thu, 21 Nov 2024 11:22:48 +0100
From: Jan Kara <jack@...e.cz>
To: Josef Bacik <josef@...icpanda.com>
Cc: kernel-team@...com, linux-fsdevel@...r.kernel.org, jack@...e.cz,
	amir73il@...il.com, brauner@...nel.org,
	torvalds@...ux-foundation.org, viro@...iv.linux.org.uk,
	linux-xfs@...r.kernel.org, linux-btrfs@...r.kernel.org,
	linux-mm@...ck.org, linux-ext4@...r.kernel.org
Subject: Re: [PATCH v8 17/19] xfs: add pre-content fsnotify hook for write
 faults

On Fri 15-11-24 10:30:30, Josef Bacik wrote:
> xfs has it's own handling for write faults, so we need to add the
> pre-content fsnotify hook for this case.  Reads go through filemap_fault
> so they're handled properly there.
> 
> Signed-off-by: Josef Bacik <josef@...icpanda.com>

This was missing proper handling for DAX read faults. What I've ended up
with is:

        struct xfs_inode        *ip = XFS_I(file_inode(vmf->vma->vm_file));
        vm_fault_t              ret;
 
+       ret = filemap_fsnotify_fault(vmf);
+       if (unlikely(ret))
+               return ret;
        xfs_ilock(ip, XFS_MMAPLOCK_SHARED);
        ret = xfs_dax_fault_locked(vmf, order, false);
        xfs_iunlock(ip, XFS_MMAPLOCK_SHARED);
@@ -1412,6 +1415,17 @@ xfs_write_fault(
        unsigned int            lock_mode = XFS_MMAPLOCK_SHARED;
        vm_fault_t              ret;
 
+       /*
+        * Usually we get here from ->page_mkwrite callback but in case of DAX
+        * we will get here also for ordinary write fault. Handle HSM
+        * notifications for that case.
+        */
+       if (IS_DAX(inode)) {
+               ret = filemap_fsnotify_fault(vmf);
+               if (unlikely(ret))
+                       return ret;
+       }
+
        sb_start_pagefault(inode->i_sb);
        file_update_time(vmf->vma->vm_file);

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR