Currently, the code reserves/releases extents in multiples of PAGE_CACHE_SIZE
units. Fix this by doing reservation/releases in block size units.

Signed-off-by: Chandan Rajendra <chan...@linux.vnet.ibm.com>
---
 fs/btrfs/file.c | 40 ++++++++++++++++++++++++++++------------
 1 file changed, 28 insertions(+), 12 deletions(-)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 795d754..e3b2b3c 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1362,16 +1362,19 @@ fail:
 static noinline int
 lock_and_cleanup_extent_if_need(struct inode *inode, struct page **pages,
                                size_t num_pages, loff_t pos,
+                               size_t write_bytes,
                                u64 *lockstart, u64 *lockend,
                                struct extent_state **cached_state)
 {
+       struct btrfs_root *root = BTRFS_I(inode)->root;
        u64 start_pos;
        u64 last_pos;
        int i;
        int ret = 0;
 
-       start_pos = pos & ~((u64)PAGE_CACHE_SIZE - 1);
-       last_pos = start_pos + ((u64)num_pages << PAGE_CACHE_SHIFT) - 1;
+       start_pos = pos & ~((u64)root->sectorsize - 1);
+       last_pos = start_pos
+               + ALIGN(pos + write_bytes - start_pos, root->sectorsize) - 1;
 
        if (start_pos < inode->i_size) {
                struct btrfs_ordered_extent *ordered;
@@ -1489,6 +1492,7 @@ static noinline ssize_t __btrfs_buffered_write(struct 
file *file,
 
        while (iov_iter_count(i) > 0) {
                size_t offset = pos & (PAGE_CACHE_SIZE - 1);
+               size_t sector_offset;
                size_t write_bytes = min(iov_iter_count(i),
                                         nrptrs * (size_t)PAGE_CACHE_SIZE -
                                         offset);
@@ -1497,6 +1501,8 @@ static noinline ssize_t __btrfs_buffered_write(struct 
file *file,
                size_t reserve_bytes;
                size_t dirty_pages;
                size_t copied;
+               size_t dirty_sectors;
+               size_t num_sectors;
 
                WARN_ON(num_pages > nrptrs);
 
@@ -1509,8 +1515,12 @@ static noinline ssize_t __btrfs_buffered_write(struct 
file *file,
                        break;
                }
 
-               reserve_bytes = num_pages << PAGE_CACHE_SHIFT;
+               sector_offset = pos & (root->sectorsize - 1);
+               reserve_bytes = ALIGN(write_bytes + sector_offset,
+                               root->sectorsize);
+
                ret = btrfs_check_data_free_space(inode, reserve_bytes, 
write_bytes);
+
                if (ret == -ENOSPC &&
                    (BTRFS_I(inode)->flags & (BTRFS_INODE_NODATACOW |
                                              BTRFS_INODE_PREALLOC))) {
@@ -1523,7 +1533,9 @@ static noinline ssize_t __btrfs_buffered_write(struct 
file *file,
                                 */
                                num_pages = DIV_ROUND_UP(write_bytes + offset,
                                                         PAGE_CACHE_SIZE);
-                               reserve_bytes = num_pages << PAGE_CACHE_SHIFT;
+                               reserve_bytes = ALIGN(write_bytes + 
sector_offset,
+                                               root->sectorsize);
+
                                ret = 0;
                        } else {
                                ret = -ENOSPC;
@@ -1558,8 +1570,8 @@ again:
                        break;
 
                ret = lock_and_cleanup_extent_if_need(inode, pages, num_pages,
-                                                     pos, &lockstart, &lockend,
-                                                     &cached_state);
+                                               pos, write_bytes, &lockstart,
+                                               &lockend, &cached_state);
                if (ret < 0) {
                        if (ret == -EAGAIN)
                                goto again;
@@ -1595,9 +1607,14 @@ again:
                 * we still have an outstanding extent for the chunk we actually
                 * managed to copy.
                 */
-               if (num_pages > dirty_pages) {
-                       release_bytes = (num_pages - dirty_pages) <<
-                               PAGE_CACHE_SHIFT;
+               num_sectors = reserve_bytes >> inode->i_blkbits;
+               dirty_sectors = round_up(copied + sector_offset,
+                                       root->sectorsize);
+               dirty_sectors >>= inode->i_blkbits;
+
+               if (num_sectors > dirty_sectors) {
+                       release_bytes = (write_bytes - copied)
+                               & ~((u64)root->sectorsize - 1);
                        if (copied > 0) {
                                spin_lock(&BTRFS_I(inode)->lock);
                                BTRFS_I(inode)->outstanding_extents++;
@@ -1611,7 +1628,7 @@ again:
                                                             release_bytes);
                }
 
-               release_bytes = dirty_pages << PAGE_CACHE_SHIFT;
+               release_bytes = ALIGN(copied + sector_offset, root->sectorsize);
 
                if (copied > 0)
                        ret = btrfs_dirty_pages(root, inode, pages,
@@ -1632,8 +1649,7 @@ again:
 
                if (only_release_metadata && copied > 0) {
                        lockstart = round_down(pos, root->sectorsize);
-                       lockend = lockstart +
-                               (dirty_pages << PAGE_CACHE_SHIFT) - 1;
+                       lockend = round_up(pos + copied, root->sectorsize) - 1;
 
                        set_extent_bit(&BTRFS_I(inode)->io_tree, lockstart,
                                       lockend, EXTENT_NORESERVE, NULL,
-- 
2.1.0

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