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fs: Introduce filemap_range_has_page()

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filemap_range_has_page() return true if the file's mapping has
a page within the range mentioned. This function will be used
to check if a write() call will cause a writeback of previous
writes.

Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Signed-off-by: Goldwyn Rodrigues <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Goldwyn Rodrigues 2017-06-20 07:05:41 -05:00 • committed by Jens Axboe
commit 7fc9e47224
2 changed files with 34 additions and 0 deletions
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32
mm/filemap.c
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@ -376,6 +376,38 @@ int filemap_flush(struct address_space *mapping)
}
EXPORT_SYMBOL(filemap_flush);
/**
* filemap_range_has_page - check if a page exists in range.
* @mapping: address space within which to check
* @start_byte: offset in bytes where the range starts
* @end_byte: offset in bytes where the range ends (inclusive)
*
* Find at least one page in the range supplied, usually used to check if
* direct writing in this range will trigger a writeback.
*/
bool filemap_range_has_page(struct address_space *mapping,
loff_t start_byte, loff_t end_byte)
{
pgoff_t index = start_byte >> PAGE_SHIFT;
pgoff_t end = end_byte >> PAGE_SHIFT;
struct pagevec pvec;
bool ret;
if (end_byte < start_byte)
return false;
if (mapping->nrpages == 0)
return false;
pagevec_init(&pvec, 0);
if (!pagevec_lookup(&pvec, mapping, index, 1))
return false;
ret = (pvec.pages[0]->index <= end);
pagevec_release(&pvec);
return ret;
}
EXPORT_SYMBOL(filemap_range_has_page);
static int __filemap_fdatawait_range(struct address_space *mapping,
loff_t start_byte, loff_t end_byte)
{