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pnfs: prepare layout under a single lock

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when starting io, both pnfs_read() and pnfs_write() need a guarantee that their range is covered by layout segments.  because we have to drop the lock for LAYOUTGET and GETDEVICEINFO, earlier layout segments may be recalled during this process.  to avoid this, new function pnfs_layout_state_prepare() gets called repeatedly until it can verify under a single lock that 1) the entire desired range is covered with layouts and 2) each of these layouts has an associated device.  whenever pnfs_layout_state_prepare() has to drop its lock for LAYOUTGET or GETDEVICEINFO, it returns PNFS_PENDING

on PNFS_SUCCESS, the caller knows that all segments in the range are valid and can dispatch io to those segments without worrying about recalls, because it still holds the pnfs_layout_state lock

Signed-off-by: Casey Bodley <cbodley@citi.umich.edu>
This commit is contained in:
Casey Bodley 2012-01-10 16:15:49 -05:00 • committed by unknown
parent c66771cda6
commit 91609640df
4 changed files with 256 additions and 276 deletions
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16
daemon/pnfs.h
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@ -257,10 +257,17 @@ void pnfs_layout_list_free(
enum pnfs_status pnfs_layout_state_open(
IN struct __nfs41_open_state *state,
OUT pnfs_layout_state **layout_out);
/* expects caller to hold an exclusive lock on pnfs_layout_state */
enum pnfs_status pnfs_layout_state_prepare(
IN pnfs_layout_state *state,
IN struct __nfs41_session *session,
IN nfs41_path_fh *meta_file,
IN struct __stateid_arg *stateid,
IN enum pnfs_iomode iomode,
IN uint64_t offset,
IN uint64_t length,
OUT pnfs_layout_state **layout_out);
IN uint64_t length);
void pnfs_layout_state_close(
IN struct __nfs41_session *session,
@ -271,6 +278,7 @@ enum pnfs_status pnfs_file_layout_recall(
IN struct __nfs41_client *client,
IN const struct cb_layoutrecall_args *recall);
/* expects caller to hold an exclusive lock on pnfs_layout_state */
enum pnfs_status pnfs_layout_io_start(
IN pnfs_layout_state *state);
@ -361,7 +369,7 @@ __inline uint32_t data_server_index(
enum pnfs_status pnfs_read(
IN struct __nfs41_root *root,
IN struct __nfs41_open_state *state,
IN const struct __stateid_arg *stateid,
IN struct __stateid_arg *stateid,
IN pnfs_layout_state *layout,
IN uint64_t offset,
IN uint64_t length,
@ -371,7 +379,7 @@ enum pnfs_status pnfs_read(
enum pnfs_status pnfs_write(
IN struct __nfs41_root *root,
IN struct __nfs41_open_state *state,
IN const struct __stateid_arg *stateid,
IN struct __stateid_arg *stateid,
IN pnfs_layout_state *layout,
IN uint64_t offset,
IN uint64_t length,