diff options
author | Martin Waitz <tali@admingilde.org> | 2005-05-01 11:59:26 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-05-01 11:59:26 -0400 |
commit | 67be2dd1bace0ec7ce2dbc1bba3f8df3d7be597e (patch) | |
tree | 317d114a0288d3b19ef9902f94b536a5a8731dbd /fs/mpage.c | |
parent | 6013d5445f9a6d0b28090027868f455c5012d1cc (diff) |
[PATCH] DocBook: fix some descriptions
Some KernelDoc descriptions are updated to match the current code.
No code changes.
Signed-off-by: Martin Waitz <tali@admingilde.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs/mpage.c')
-rw-r--r-- | fs/mpage.c | 92 |
1 files changed, 46 insertions, 46 deletions
diff --git a/fs/mpage.c b/fs/mpage.c index 3923facf94eb..32c7c8fcfce7 100644 --- a/fs/mpage.c +++ b/fs/mpage.c | |||
@@ -160,52 +160,6 @@ map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block) | |||
160 | } while (page_bh != head); | 160 | } while (page_bh != head); |
161 | } | 161 | } |
162 | 162 | ||
163 | /** | ||
164 | * mpage_readpages - populate an address space with some pages, and | ||
165 | * start reads against them. | ||
166 | * | ||
167 | * @mapping: the address_space | ||
168 | * @pages: The address of a list_head which contains the target pages. These | ||
169 | * pages have their ->index populated and are otherwise uninitialised. | ||
170 | * | ||
171 | * The page at @pages->prev has the lowest file offset, and reads should be | ||
172 | * issued in @pages->prev to @pages->next order. | ||
173 | * | ||
174 | * @nr_pages: The number of pages at *@pages | ||
175 | * @get_block: The filesystem's block mapper function. | ||
176 | * | ||
177 | * This function walks the pages and the blocks within each page, building and | ||
178 | * emitting large BIOs. | ||
179 | * | ||
180 | * If anything unusual happens, such as: | ||
181 | * | ||
182 | * - encountering a page which has buffers | ||
183 | * - encountering a page which has a non-hole after a hole | ||
184 | * - encountering a page with non-contiguous blocks | ||
185 | * | ||
186 | * then this code just gives up and calls the buffer_head-based read function. | ||
187 | * It does handle a page which has holes at the end - that is a common case: | ||
188 | * the end-of-file on blocksize < PAGE_CACHE_SIZE setups. | ||
189 | * | ||
190 | * BH_Boundary explanation: | ||
191 | * | ||
192 | * There is a problem. The mpage read code assembles several pages, gets all | ||
193 | * their disk mappings, and then submits them all. That's fine, but obtaining | ||
194 | * the disk mappings may require I/O. Reads of indirect blocks, for example. | ||
195 | * | ||
196 | * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be | ||
197 | * submitted in the following order: | ||
198 | * 12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16 | ||
199 | * because the indirect block has to be read to get the mappings of blocks | ||
200 | * 13,14,15,16. Obviously, this impacts performance. | ||
201 | * | ||
202 | * So what we do it to allow the filesystem's get_block() function to set | ||
203 | * BH_Boundary when it maps block 11. BH_Boundary says: mapping of the block | ||
204 | * after this one will require I/O against a block which is probably close to | ||
205 | * this one. So you should push what I/O you have currently accumulated. | ||
206 | * | ||
207 | * This all causes the disk requests to be issued in the correct order. | ||
208 | */ | ||
209 | static struct bio * | 163 | static struct bio * |
210 | do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages, | 164 | do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages, |
211 | sector_t *last_block_in_bio, get_block_t get_block) | 165 | sector_t *last_block_in_bio, get_block_t get_block) |
@@ -320,6 +274,52 @@ confused: | |||
320 | goto out; | 274 | goto out; |
321 | } | 275 | } |
322 | 276 | ||
277 | /** | ||
278 | * mpage_readpages - populate an address space with some pages, and | ||
279 | * start reads against them. | ||
280 | * | ||
281 | * @mapping: the address_space | ||
282 | * @pages: The address of a list_head which contains the target pages. These | ||
283 | * pages have their ->index populated and are otherwise uninitialised. | ||
284 | * | ||
285 | * The page at @pages->prev has the lowest file offset, and reads should be | ||
286 | * issued in @pages->prev to @pages->next order. | ||
287 | * | ||
288 | * @nr_pages: The number of pages at *@pages | ||
289 | * @get_block: The filesystem's block mapper function. | ||
290 | * | ||
291 | * This function walks the pages and the blocks within each page, building and | ||
292 | * emitting large BIOs. | ||
293 | * | ||
294 | * If anything unusual happens, such as: | ||
295 | * | ||
296 | * - encountering a page which has buffers | ||
297 | * - encountering a page which has a non-hole after a hole | ||
298 | * - encountering a page with non-contiguous blocks | ||
299 | * | ||
300 | * then this code just gives up and calls the buffer_head-based read function. | ||
301 | * It does handle a page which has holes at the end - that is a common case: | ||
302 | * the end-of-file on blocksize < PAGE_CACHE_SIZE setups. | ||
303 | * | ||
304 | * BH_Boundary explanation: | ||
305 | * | ||
306 | * There is a problem. The mpage read code assembles several pages, gets all | ||
307 | * their disk mappings, and then submits them all. That's fine, but obtaining | ||
308 | * the disk mappings may require I/O. Reads of indirect blocks, for example. | ||
309 | * | ||
310 | * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be | ||
311 | * submitted in the following order: | ||
312 | * 12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16 | ||
313 | * because the indirect block has to be read to get the mappings of blocks | ||
314 | * 13,14,15,16. Obviously, this impacts performance. | ||
315 | * | ||
316 | * So what we do it to allow the filesystem's get_block() function to set | ||
317 | * BH_Boundary when it maps block 11. BH_Boundary says: mapping of the block | ||
318 | * after this one will require I/O against a block which is probably close to | ||
319 | * this one. So you should push what I/O you have currently accumulated. | ||
320 | * | ||
321 | * This all causes the disk requests to be issued in the correct order. | ||
322 | */ | ||
323 | int | 323 | int |
324 | mpage_readpages(struct address_space *mapping, struct list_head *pages, | 324 | mpage_readpages(struct address_space *mapping, struct list_head *pages, |
325 | unsigned nr_pages, get_block_t get_block) | 325 | unsigned nr_pages, get_block_t get_block) |