NTFS: - Modify ->readpage and ->writepage (fs/ntfs/aops.c) so they detect

        and handle the case where an attribute is converted from resident
        to non-resident by a concurrent file write.
      - Reorder some operations when converting an attribute from resident
        to non-resident (fs/ntfs/attrib.c) so it is safe wrt concurrent
        ->readpage and ->writepage.

Signed-off-by: Anton Altaparmakov <aia21@cantab.net>

3 files changed, 46 insertions, 16 deletions

diff --git a/fs/ntfs/ChangeLog b/fs/ntfs/ChangeLog
index e0b4adf5adce..b29e0618f358 100644
--- a/fs/ntfs/ChangeLog
+++ b/fs/ntfs/ChangeLog
@@ -100,6 +100,9 @@ ToDo/Notes:
         - Add fs/ntfs/attrib.[hc]::ntfs_attr_make_non_resident().
         - Fix sign of various error return values to be negative in
           fs/ntfs/lcnalloc.c.
+        - Modify ->readpage and ->writepage (fs/ntfs/aops.c) so they detect and
+          handle the case where an attribute is converted from resident to
+          non-resident by a concurrent file write.
 
 2.1.22 - Many bug and race fixes and error handling improvements.
 
diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index 2a7cba258cca..6241c4cfbe28 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -355,6 +355,7 @@ static int ntfs_readpage(struct file *file, struct page *page)
         u32 attr_len;
         int err = 0;
 
+retry_readpage:
         BUG_ON(!PageLocked(page));
         /*
          * This can potentially happen because we clear PageUptodate() during
@@ -408,6 +409,14 @@ static int ntfs_readpage(struct file *file, struct page *page)
                 err = PTR_ERR(mrec);
                 goto err_out;
         }
+        /*
+         * If a parallel write made the attribute non-resident, drop the mft
+         * record and retry the readpage.
+         */
+        if (unlikely(NInoNonResident(ni))) {
+                unmap_mft_record(base_ni);
+                goto retry_readpage;
+        }
         ctx = ntfs_attr_get_search_ctx(base_ni, mrec);
         if (unlikely(!ctx)) {
                 err = -ENOMEM;
@@ -1248,6 +1257,7 @@ static int ntfs_writepage(struct page *page, struct writeback_control *wbc)
         u32 attr_len;
         int err;
 
+retry_writepage:
         BUG_ON(!PageLocked(page));
         i_size = i_size_read(vi);
         /* Is the page fully outside i_size? (truncate in progress) */
@@ -1338,6 +1348,14 @@ static int ntfs_writepage(struct page *page, struct writeback_control *wbc)
                 ctx = NULL;
                 goto err_out;
         }
+        /*
+         * If a parallel write made the attribute non-resident, drop the mft
+         * record and retry the writepage.
+         */
+        if (unlikely(NInoNonResident(ni))) {
+                unmap_mft_record(base_ni);
+                goto retry_writepage;
+        }
         ctx = ntfs_attr_get_search_ctx(base_ni, m);
         if (unlikely(!ctx)) {
                 err = -ENOMEM;
diff --git a/fs/ntfs/attrib.c b/fs/ntfs/attrib.c
index 3b9de4040216..41859343a0c8 100644
--- a/fs/ntfs/attrib.c
+++ b/fs/ntfs/attrib.c
@@ -1376,19 +1376,6 @@ int ntfs_attr_make_non_resident(ntfs_inode *ni)
         err = ntfs_attr_record_resize(m, a, arec_size);
         if (unlikely(err))
                 goto err_out;
-        /* Setup the in-memory attribute structure to be non-resident. */
-        NInoSetNonResident(ni);
-        ni->runlist.rl = rl;
-        write_lock_irqsave(&ni->size_lock, flags);
-        ni->allocated_size = new_size;
-        write_unlock_irqrestore(&ni->size_lock, flags);
-        /*
-         * FIXME: For now just clear all of these as we do not support them
-         * when writing.
-         */
-        NInoClearCompressed(ni);
-        NInoClearSparse(ni);
-        NInoClearEncrypted(ni);
         /*
          * Convert the resident part of the attribute record to describe a
          * non-resident attribute.
@@ -1399,7 +1386,10 @@ int ntfs_attr_make_non_resident(ntfs_inode *ni)
                 memmove((u8*)a + name_ofs, (u8*)a + le16_to_cpu(a->name_offset),
                                 a->name_length * sizeof(ntfschar));
         a->name_offset = cpu_to_le16(name_ofs);
-        /* Update the flags to match the in-memory ones. */
+        /*
+         * FIXME: For now just clear all of these as we do not support them
+         * when writing.
+         */
         a->flags &= cpu_to_le16(0xffff & ~le16_to_cpu(ATTR_IS_SPARSE |
                         ATTR_IS_ENCRYPTED | ATTR_COMPRESSION_MASK));
         /* Setup the fields specific to non-resident attributes. */
@@ -1422,6 +1412,25 @@ int ntfs_attr_make_non_resident(ntfs_inode *ni)
                                 err);
                 goto undo_err_out;
         }
+        /* Setup the in-memory attribute structure to be non-resident. */
+        /*
+         * FIXME: For now just clear all of these as we do not support them
+         * when writing.
+         */
+        NInoClearSparse(ni);
+        NInoClearEncrypted(ni);
+        NInoClearCompressed(ni);
+        ni->runlist.rl = rl;
+        write_lock_irqsave(&ni->size_lock, flags);
+        ni->allocated_size = new_size;
+        write_unlock_irqrestore(&ni->size_lock, flags);
+        /*
+         * This needs to be last since the address space operations ->readpage
+         * and ->writepage can run concurrently with us as they are not
+         * serialized on i_sem.  Note, we are not allowed to fail once we flip
+         * this switch, which is another reason to do this last.
+         */
+        NInoSetNonResident(ni);
         /* Mark the mft record dirty, so it gets written back. */
         flush_dcache_mft_record_page(ctx->ntfs_ino);
         mark_mft_record_dirty(ctx->ntfs_ino);
@@ -1431,6 +1440,7 @@ int ntfs_attr_make_non_resident(ntfs_inode *ni)
         if (page) {
                 set_page_dirty(page);
                 unlock_page(page);
+                mark_page_accessed(page);
                 page_cache_release(page);
         }
         ntfs_debug("Done.");
@@ -1492,11 +1502,10 @@ undo_err_out:
                 memcpy((u8*)a + mp_ofs, kaddr, attr_size);
                 kunmap_atomic(kaddr, KM_USER0);
         }
-        /* Finally setup the ntfs inode appropriately. */
+        /* Setup the allocated size in the ntfs inode in case it changed. */
         write_lock_irqsave(&ni->size_lock, flags);
         ni->allocated_size = arec_size - mp_ofs;
         write_unlock_irqrestore(&ni->size_lock, flags);
-        NInoClearNonResident(ni);
         /* Mark the mft record dirty, so it gets written back. */
         flush_dcache_mft_record_page(ctx->ntfs_ino);
         mark_mft_record_dirty(ctx->ntfs_ino);