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authorChris Mason <chris.mason@oracle.com>2011-02-10 12:35:00 -0500
committerChris Mason <chris.mason@oracle.com>2011-02-14 13:03:52 -0500
commiteb14ab8ed24a0405fd056068b28c33a1cd846024 (patch)
tree1451cad453a3ff66bc5369dc83daf7e3a50c4897 /fs/btrfs/extent_io.c
parent3a90983dbdcb2f4f48c0d771d8e5b4d88f27fae6 (diff)
Btrfs: fix page->private races
There is a race where btrfs_releasepage can drop the page->private contents just as alloc_extent_buffer is setting up pages for metadata. Because of how the Btrfs page flags work, this results in us skipping the crc on the page during IO. This patch sovles the race by waiting until after the extent buffer is inserted into the radix tree before it sets page private. Signed-off-by: Chris Mason <chris.mason@oracle.com>
Diffstat (limited to 'fs/btrfs/extent_io.c')
-rw-r--r--fs/btrfs/extent_io.c38
1 files changed, 35 insertions, 3 deletions
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 8862dda46ff6..0418bf2c9757 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -1946,6 +1946,7 @@ void set_page_extent_mapped(struct page *page)
1946 1946
1947static void set_page_extent_head(struct page *page, unsigned long len) 1947static void set_page_extent_head(struct page *page, unsigned long len)
1948{ 1948{
1949 WARN_ON(!PagePrivate(page));
1949 set_page_private(page, EXTENT_PAGE_PRIVATE_FIRST_PAGE | len << 2); 1950 set_page_private(page, EXTENT_PAGE_PRIVATE_FIRST_PAGE | len << 2);
1950} 1951}
1951 1952
@@ -3195,7 +3196,13 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
3195 } 3196 }
3196 if (!PageUptodate(p)) 3197 if (!PageUptodate(p))
3197 uptodate = 0; 3198 uptodate = 0;
3198 unlock_page(p); 3199
3200 /*
3201 * see below about how we avoid a nasty race with release page
3202 * and why we unlock later
3203 */
3204 if (i != 0)
3205 unlock_page(p);
3199 } 3206 }
3200 if (uptodate) 3207 if (uptodate)
3201 set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags); 3208 set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
@@ -3219,9 +3226,26 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
3219 atomic_inc(&eb->refs); 3226 atomic_inc(&eb->refs);
3220 spin_unlock(&tree->buffer_lock); 3227 spin_unlock(&tree->buffer_lock);
3221 radix_tree_preload_end(); 3228 radix_tree_preload_end();
3229
3230 /*
3231 * there is a race where release page may have
3232 * tried to find this extent buffer in the radix
3233 * but failed. It will tell the VM it is safe to
3234 * reclaim the, and it will clear the page private bit.
3235 * We must make sure to set the page private bit properly
3236 * after the extent buffer is in the radix tree so
3237 * it doesn't get lost
3238 */
3239 set_page_extent_mapped(eb->first_page);
3240 set_page_extent_head(eb->first_page, eb->len);
3241 if (!page0)
3242 unlock_page(eb->first_page);
3222 return eb; 3243 return eb;
3223 3244
3224free_eb: 3245free_eb:
3246 if (eb->first_page && !page0)
3247 unlock_page(eb->first_page);
3248
3225 if (!atomic_dec_and_test(&eb->refs)) 3249 if (!atomic_dec_and_test(&eb->refs))
3226 return exists; 3250 return exists;
3227 btrfs_release_extent_buffer(eb); 3251 btrfs_release_extent_buffer(eb);
@@ -3272,10 +3296,11 @@ int clear_extent_buffer_dirty(struct extent_io_tree *tree,
3272 continue; 3296 continue;
3273 3297
3274 lock_page(page); 3298 lock_page(page);
3299 WARN_ON(!PagePrivate(page));
3300
3301 set_page_extent_mapped(page);
3275 if (i == 0) 3302 if (i == 0)
3276 set_page_extent_head(page, eb->len); 3303 set_page_extent_head(page, eb->len);
3277 else
3278 set_page_private(page, EXTENT_PAGE_PRIVATE);
3279 3304
3280 clear_page_dirty_for_io(page); 3305 clear_page_dirty_for_io(page);
3281 spin_lock_irq(&page->mapping->tree_lock); 3306 spin_lock_irq(&page->mapping->tree_lock);
@@ -3465,6 +3490,13 @@ int read_extent_buffer_pages(struct extent_io_tree *tree,
3465 3490
3466 for (i = start_i; i < num_pages; i++) { 3491 for (i = start_i; i < num_pages; i++) {
3467 page = extent_buffer_page(eb, i); 3492 page = extent_buffer_page(eb, i);
3493
3494 WARN_ON(!PagePrivate(page));
3495
3496 set_page_extent_mapped(page);
3497 if (i == 0)
3498 set_page_extent_head(page, eb->len);
3499
3468 if (inc_all_pages) 3500 if (inc_all_pages)
3469 page_cache_get(page); 3501 page_cache_get(page);
3470 if (!PageUptodate(page)) { 3502 if (!PageUptodate(page)) {