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-rw-r--r--Documentation/block/biodoc.txt10
1 files changed, 5 insertions, 5 deletions
diff --git a/Documentation/block/biodoc.txt b/Documentation/block/biodoc.txt
index 34bf8f60d8f8..c6c9a9c10d7f 100644
--- a/Documentation/block/biodoc.txt
+++ b/Documentation/block/biodoc.txt
@@ -183,7 +183,7 @@ it, the pci dma mapping routines and associated data structures have now been
183modified to accomplish a direct page -> bus translation, without requiring 183modified to accomplish a direct page -> bus translation, without requiring
184a virtual address mapping (unlike the earlier scheme of virtual address 184a virtual address mapping (unlike the earlier scheme of virtual address
185-> bus translation). So this works uniformly for high-memory pages (which 185-> bus translation). So this works uniformly for high-memory pages (which
186do not have a correponding kernel virtual address space mapping) and 186do not have a corresponding kernel virtual address space mapping) and
187low-memory pages. 187low-memory pages.
188 188
189Note: Please refer to DMA-mapping.txt for a discussion on PCI high mem DMA 189Note: Please refer to DMA-mapping.txt for a discussion on PCI high mem DMA
@@ -391,7 +391,7 @@ forced such requests to be broken up into small chunks before being passed
391on to the generic block layer, only to be merged by the i/o scheduler 391on to the generic block layer, only to be merged by the i/o scheduler
392when the underlying device was capable of handling the i/o in one shot. 392when the underlying device was capable of handling the i/o in one shot.
393Also, using the buffer head as an i/o structure for i/os that didn't originate 393Also, using the buffer head as an i/o structure for i/os that didn't originate
394from the buffer cache unecessarily added to the weight of the descriptors 394from the buffer cache unnecessarily added to the weight of the descriptors
395which were generated for each such chunk. 395which were generated for each such chunk.
396 396
397The following were some of the goals and expectations considered in the 397The following were some of the goals and expectations considered in the
@@ -403,14 +403,14 @@ i. Should be appropriate as a descriptor for both raw and buffered i/o -
403 for raw i/o. 403 for raw i/o.
404ii. Ability to represent high-memory buffers (which do not have a virtual 404ii. Ability to represent high-memory buffers (which do not have a virtual
405 address mapping in kernel address space). 405 address mapping in kernel address space).
406iii.Ability to represent large i/os w/o unecessarily breaking them up (i.e 406iii.Ability to represent large i/os w/o unnecessarily breaking them up (i.e
407 greater than PAGE_SIZE chunks in one shot) 407 greater than PAGE_SIZE chunks in one shot)
408iv. At the same time, ability to retain independent identity of i/os from 408iv. At the same time, ability to retain independent identity of i/os from
409 different sources or i/o units requiring individual completion (e.g. for 409 different sources or i/o units requiring individual completion (e.g. for
410 latency reasons) 410 latency reasons)
411v. Ability to represent an i/o involving multiple physical memory segments 411v. Ability to represent an i/o involving multiple physical memory segments
412 (including non-page aligned page fragments, as specified via readv/writev) 412 (including non-page aligned page fragments, as specified via readv/writev)
413 without unecessarily breaking it up, if the underlying device is capable of 413 without unnecessarily breaking it up, if the underlying device is capable of
414 handling it. 414 handling it.
415vi. Preferably should be based on a memory descriptor structure that can be 415vi. Preferably should be based on a memory descriptor structure that can be
416 passed around different types of subsystems or layers, maybe even 416 passed around different types of subsystems or layers, maybe even
@@ -1013,7 +1013,7 @@ Characteristics:
1013i. Binary tree 1013i. Binary tree
1014AS and deadline i/o schedulers use red black binary trees for disk position 1014AS and deadline i/o schedulers use red black binary trees for disk position
1015sorting and searching, and a fifo linked list for time-based searching. This 1015sorting and searching, and a fifo linked list for time-based searching. This
1016gives good scalability and good availablility of information. Requests are 1016gives good scalability and good availability of information. Requests are
1017almost always dispatched in disk sort order, so a cache is kept of the next 1017almost always dispatched in disk sort order, so a cache is kept of the next
1018request in sort order to prevent binary tree lookups. 1018request in sort order to prevent binary tree lookups.
1019 1019